root/trunk/data/doc/manual.docbook @ 1011

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC '-//OASIS//DTD DocBook V4.0//EN'
               'http://www.oasis-open.org/docbook/xml/4.0/docbookx.dtd'>
<book id="Hydrogen-manual" lang="en">

<bookinfo>
        <title>Hydrogen Manual</title>
        <authorgroup>
                <author>
                        <firstname>Antonio</firstname>
                        <surname>Piraino</surname>
                </author>
                <author>
                        <firstname>Alessandro</firstname>
                        <surname>Cominu</surname>
                </author>
        </authorgroup>

        <date>22/may/2005</date>

        <abstract>
                <para>
                        Hydrogen is a software synthesizer which can be used alone, emulating a drum machine based on patterns, or via an external MIDI keyboard/sequencer software. Hydrogen compiles on Linux/x86 and Mac OS X, although the latter is still experimental, so ask in the developers mailing list for further details.
                </para>
        </abstract>
</bookinfo>

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# PRIMO CAPITOLO  #
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<chapter id="chap.introduction">
        <title>Introduction</title>

        <section id="sect.download">
                <title>Download</title>
                <para>
                        The latest stable version of hydrogen is available as a tarball at
                        <ulink url="http://www.hydrogen-music.org/?p=download">http://www.hydrogen-music.org</ulink>.
                </para>
                <para>
                        It is possible to download the latest source files directly from our subversion server with:
                
                        <screen><prompt>$</prompt> <command>svn co http://svn.assembla.com/svn/hydrogen/trunk</command></screen>
                        
                        A certain release can be fetched with:
                         <screen><prompt>$</prompt> <command>svn co http://svn.assembla.com/svn/hydrogen/tags/0.9.3</command></screen>                                      
                </para>
                
                <para>
                        Compiling Hydrogen depends on the following libraries:
                        <itemizedlist mark="opencircle">
                                <listitem>
                                        <para>qt (>= 4.0) at <ulink url="http://www.trolltech.com"/></para>
                                </listitem>
                                <listitem>
                                        <para>libsndfile at <ulink url="http://www.mega-nerd.com/libsndfile/"/></para>
                                </listitem>

                                <listitem>
                                        <para>ALSA (>= 1.x) at <ulink url="http://www.alsa-project.com"/> (only if you wish to use ALSA as audio driver)</para>
                                </listitem>
                                <listitem>
                                        <para>Jack Audio Connection Kit (>= 0.80) at <ulink url="http://jackaudio.org/"/> (only if you wish to use Jack as audio driver)</para>
                                </listitem>
                                 <listitem>
                                        <para>PortAudio at <ulink url="http://www.portaudio.com"/> (only if you wish to use PortAudio as audio driver)</para>
                                </listitem>
                                 <listitem>
                                        <para>Flac at <ulink url="http://flac.sf.net"/> (only if you wish to use flac samples)</para>
                                </listitem>
                                 <listitem>
                                        <para>ladspa at <ulink url="http://ladspa.org"/> (only if you wish to use ladspa effects)</para>
                                </listitem>
                                 <listitem>
                                        <para>liblrdf at <ulink url="http://liblrdf.sf.net"/> (only if you wish to use lrdf to categorise effects)</para>
                                </listitem>
                                 <listitem>
                                        <para>lash at <ulink url="http://lash.nongnu.org"/> (only if you wish to use lash)</para>
                                </listitem>
                        </itemizedlist>
                        Please install them with your distribution's package manager. If you're running a debian-based system,
                        you can install the libraries with:
                        <screen>
        <prompt>$</prompt> <command>apt-get install libqt4-dev g++ libasound2-dev \
        libjack-dev liblrdf0-dev libflac++-dev libtar-dev libsndfile1-dev \
        liblash-dev libportaudio-dev libportmidi-dev </command></screen> 
        </para>
        </section>

        <section id="sect.compilation">
                <title>Build</title>
                <para>
                            Decompress the tarball or go to the directory where the subversion copy was checked out:
                    <screen>
        <prompt>$</prompt> <command>cd hydrogen-*</command>
        <prompt>$</prompt> <command>scons</command>
        <prompt>$</prompt> <command>su -c "scons install"</command>
                    </screen>
                </para>

                <para>
                    Before compiling, check for additional options with:
                    <screen>
        <prompt>$</prompt> <command>scons --help</command>
                    </screen>
                    
                    If you want to use features which are not enabled by default (for instance PortAudio), you can enable them with:
                    <screen>
        <prompt>$</prompt> <command>scons portaudio=1</command>
                    </screen>
                    
                    Namely, if you get some error while running Hydrogen and you want to report it remember to configure hydrogen with:
                    <screen>
        <prompt>$</prompt> <command>scons debug=1</command>
                    </screen>
                    
                    To clean up compiled code:
                    <screen>
        <prompt>$</prompt> <command>scons -c</command>
                    </screen>
                </para>
        </section>

<!-- prokoudine ?
        <section id="sect.basics">
                <title>[TODO] BASICS</title>
                <para>
                explain and develop basics about the technology behind software of this kind
                </para>
        </section>
-->

        <!--
        
        mauser: In my opionon those driver informations are unnecessary here, moved to audio tab
        
        
        <section id="sect.config_audio_driver">
                <title>Audio driver configuration</title>
                <para>
                        It's very important to choose the proper audio driver for our system, since 
                        the choice may influence quite much general performances. The choice is between
                        Oss audio driver, ALSA, PortAudio, CoreAudio and Jack audio driver.
                </para>
                
                <section id="sect.driver.jack">
                        <title>Jack audio driver</title>
                        <para>
                        The Jack driver is a professional audio server which permits very low lag and exchanges with other
                        audio software. <emphasis>We strongly recommend using this driver to have the best out of Hydrogen</emphasis>.
                        JACK server will start automatically if not already running.
                        </para>
                </section>
                
                <section id="sect.driver.alsa">
                        <title>ALSA audio driver</title>
                        <para>
                        the widely adopted Linux standard audio drivers
                        </para>
                </section>
                
                <section id="sect.driver.oss">
                        <title>OSS audio driver</title>
                        <para>
                        The Oss audio driver uses /dev/dsp and it's based on the OSS interface which is
                        supported by the vast majority of sound cards available for linux; this said, 
                        the use of this audio driver blocks /dev/dsp until Hydrogen is closed i.e. unusable 
                        by any other software. Use it as last resource.
                        </para>
                </section>
                
                <section id="sect.driver.portaudio">
                        <title>PortAudio audio driver</title>
                        <para>
                         an open-source multiplatform audio driver
                        </para>
                </section>
                
                <section id="sect.driver.coreaudio">
                        <title>CoreAudio audio driver</title>
                        <para>
                         a driver for Mac OS X (experimental) 
                        </para>
                </section>
        </section>
        -->
        
        
        <section id="sect.preferences">
                <title>Audio preferences</title>
                <para>
                    First of all you should make shure that the audio engine is configured properly. 
                    The preferences dialog can be accessed via the tools menu (tools -> preferences). 
                </para>
                

                
                <section id="sect.preferences.audio_tab">
                        <title>The Audio System tab</title>
                        
                        <para>From the "Audio System" tab (<xref linkend="fig.preferences.audio_tab"/>) it is possible to modify the audio driver being used (OSS, Jack, ALSA, PortAudio) with its buffer and sampling rate (unless using JACK, in this case the audio driver configuration should happen before starting the JACK server).
                        </para>
                        <para>
                        We can set some features of Hydrogen like "Enable track outputs" useful if you want to add effects to a single instrument with jack-rack. "Connect to Default Output Pair" connects the output to the default ports: uncheck this if you want to connect JACK output to other ports without disconnecting them first
                        </para>
                        <para>
                        Keep also an eye on the value of "Polyphony": depending on your CPU you may want to change the max simultaneous notes in order to prevent hydrogen from overunning the audio driver.
                        </para>
                
                
                        
                        <figure id="fig.preferences.audio_tab">
                        <title>The Audio System Tab</title>
                        <mediaobject>
                            <imageobject>
                                    <imagedata fileref="img/PreferencesAudioSystem.png" format="PNG"/>
                            </imageobject>
                        </mediaobject>
                        </figure>
                        
                        <para>
                            The following drivers are available:
                        </para>
                        
                        <itemizedlist>

                        <listitem>
                            <para>
                            <emphasis role="bold">jackd</emphasis>: The Jack driver is a professional audio server which permits very low lag and exchanges with other
                            audio software. <emphasis>We strongly recommend using this driver to have the best out of Hydrogen</emphasis>.
                            JACK server will start automatically if not already running.
                            </para>
                        </listitem>
                
                        <listitem>
                            <para>
                            <emphasis role="bold">ALSA</emphasis>:
                            the widely adopted Linux standard audio drivers
                            </para>
                        </listitem>
                        
                        <listitem>
                            <para>
                            <emphasis role="bold">OSS</emphasis>:
                            The Oss audio driver uses /dev/dsp and it's based on the OSS interface which is
                            supported by the vast majority of sound cards available for linux; this said, 
                            the use of this audio driver blocks /dev/dsp until Hydrogen is closed i.e. unusable 
                            by any other software. Use it as last resort.
                            </para>
                        </listitem>
                
                        <listitem>
                            <para>
                            <emphasis role="bold">PortAudio</emphasis>:
                            an open-source multiplatform audio driver
                            </para>
                        </listitem>

                        <listitem>
                            <para>
                            <emphasis role="bold">CoreAudio</emphasis>:
                            a driver for Mac OS X (experimental) 
                            </para>
                        </listitem>
                    </itemizedlist>
                </section>
                
                <section id="sect.preferences.midi_tab">
                        <title>The Midi System tab</title>
                        <para>
                        The "Midi System" tab (<xref linkend="fig.preferences.midi_tab"/>) concerns the MIDI input. You can choose the MIDI driver and input, setup channels, binding actions to MIDI events.
                        </para>
                        
                        <figure id="fig.preferences.midi_tab">
                        <title>The MIDI System Tab</title>
                        <mediaobject>
                            <imageobject>
                                    <imagedata fileref="img/PreferencesMidiSystem.png" format="PNG"/>
                            </imageobject>
                        </mediaobject>
                        </figure>
                </section>
                
                <section id="sect.preferences.appearance_tab">
                    <title>The Appearance tab</title>
                    <para>
                    The "Appearance" tab (<xref linkend="fig.preferences.appearance_tab"/>) let's you to modify Hydrogen and QT graphical properties.
                    </para>
                    
                    <figure id="fig.preferences.appearance_tab">
                    <title>The Appearance Tab</title>
                    <mediaobject>
                        <imageobject>
                                <imagedata fileref="img/PreferencesAppearance.png" format="PNG"/>
                        </imageobject>
                    </mediaobject>
                    </figure>
                </section>
                
                
                <section id="sect.preferences.audio_engine_tab">
                    <title>The Audio Engine tab</title>
                    <para>
                    The audio engine info is a window with various stats about Hydrogen and the audio driver. In case JACK is used, buffer and sampling rate should be set before starting Hydrogen (JACK automatically starts when an application tries to connect).
                    </para>
                    
                    <figure id="fig.preferences.audio_engine_tab">
                    <title>The Audio Engine Info Window</title>
                    <mediaobject>
                        <imageobject>
                                <imagedata fileref="img/AudioEngineInfoDialog.png" format="PNG"/>
                        </imageobject>
                    </mediaobject>
                    </figure>
                </section>
        </section>
</chapter>

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<chapter id="chap.using_hydrogen">
        <title>Using Hydrogen</title>
        
        <section id="sect.file_types">
            <title>Used Filetypes</title>
            <para>Before working with Hydrogen, please familiarize with these filetypes:</para>
            <itemizedlist>
                    <listitem>
                        <para><emphasis role="bold">*.h2pattern</emphasis>: XML file describing a single pattern. Patterns are group of beats and are managed in the pattern editor.</para>
                    </listitem>
                    <listitem>
                        <para><emphasis role="bold">*.h2song</emphasis>: XML file describing the whole song (or sequence). Songs are group of patterns with their properties and are manager using the song editor</para>
                    </listitem>
                    <listitem>
                        <para><emphasis role="bold">*.h2playlist</emphasis>: XML file describing a playlist.A Playlist is a (ordered) group of songs.</para>
                    </listitem>
                    <listitem>
                        <para><emphasis role="bold">*.h2drumkit</emphasis>: a compressed and archived folder containing all sound samples composing a drumkit and a description XML file. Drumkits are basically group of sound samples.</para>
                    </listitem>
            </itemizedlist>
        </section>
        
        <section id="sect.main_menu">
            <title>Main menu</title>
            <para><emphasis role="bold">Projects</emphasis>: this menu offers file related functions.</para>
            <itemizedlist>

                            <listitem><para><emphasis>New</emphasis> - Create a new song</para></listitem>
                            <listitem><para><emphasis>Show Info</emphasis> - Set general properties of the song such as name, author, license and generic notes</para></listitem>
                            <listitem><para><emphasis>Open</emphasis> - Open a song</para></listitem>
                            <listitem><para><emphasis>Open Demo</emphasis> - Open a demo song (demo songs are stored in <emphasis>$INSTALLPATH/share/hydrogen/data/demo_songs</emphasis>)</para></listitem>
                            <listitem><para><emphasis>Open recent</emphasis> - Open a menu showing last used songs</para></listitem>
                            <listitem><para><emphasis>Save</emphasis> - Save changes to current song</para></listitem>
                            <listitem><para><emphasis>Save as</emphasis> - Save current song specifying a name (default path: <emphasis>$HOME/.hydrogen/data/songs)</emphasis></para></listitem>
                            <listitem><para><emphasis>Open pattern</emphasis> - Open a saved pattern belonging to the current drumkit</para></listitem>
                            <listitem><para><emphasis>Export pattern as</emphasis> - Saves a pattern. It will be stored in <emphasis>$HOME/.hydrogen/data/patterns/drumkit_name</emphasis></para></listitem>
                            <listitem><para><emphasis>Export MIDI file</emphasis> - Export current song in MIDI format</para></listitem>
                            <listitem><para><emphasis>Export song</emphasis> - Export current song in WAV format</para></listitem>
                            <listitem><para><emphasis>Quit</emphasis> - Quit Hydrogen</para></listitem>
            </itemizedlist>
            
            
                
        <para><emphasis role="bold">Instruments</emphasis>: this menu offers instruments and drumkit (sound libraries) functions.</para>
            <itemizedlist>
                        <listitem><para><emphasis>Add instrument</emphasis> - Add a new instrument to your current drumkit</para></listitem>
                        <listitem><para><emphasis>Clear all</emphasis> - Delete all instruments from the current drumkit</para></listitem>
                        <listitem><para><emphasis>Save library</emphasis> - Saves all instruments settings (and their sound samples) in <emphasis>$HOME/.hydrogen/data/library_name</emphasis></para></listitem>
                        <listitem><para><emphasis>Export library</emphasis> - Compress all instruments samples and settings in a drumkit in <emphasis>$HOME/.hydrogen/data/library_name</emphasis></para></listitem>
                        <listitem><para><emphasis>Import library</emphasis> - Imports another drumkit from the local filesystem or download it from a remote location through an XML feed. The XML file that should be provided is <emphasis role="bold">NOT</emphasis> RSS compliant (see <ulink url="http://www.hydrogen-music.org/feeds/drumkit_list.php" >Hydrogen website</ulink> for an example). To load another drumkit in your current working session of Hydrogen, read <xref linkend="sect.sound_library"/>.</para></listitem>
            </itemizedlist>
        
        
            <para><emphasis role="bold">Tools</emphasis>: opens the mixer, the playlist editor, the instrument rack and the general preferences window.</para>
            <itemizedlist>
                    <listitem><para><emphasis>Playlist editor</emphasis> - A tool to manage playlists.</para></listitem>
                    <listitem><para><emphasis>Mixer</emphasis> - Open the mixer window.</para></listitem>
                    <listitem><para><emphasis>Instrument rack</emphasis> - Open the instrument rack panel.</para></listitem>
                    <listitem><para><emphasis>Preferences</emphasis> - Open the main preferences window. Read <xref linkend="sect.preferences"/> on how to configure Hydrogen.</para></listitem>
            </itemizedlist>
        
        
            <para><emphasis role="bold">Debug</emphasis>: tools mainly for debugging and monitoring Hydrogen (only available when compiled with debug support).</para>
            <itemizedlist>
                    <listitem><para><emphasis>Show audio engine info - </emphasis>Open a monitor with various <link linkend="sect.preferences.audio_engine_tab">stats</link></para></listitem>
                    <listitem><para><emphasis>debug action - </emphasis> Insert debug commands.</para></listitem>
                    <listitem><para><emphasis>Print Objects - </emphasis>Print on stdout current objects map.</para></listitem>
            </itemizedlist>
    
    
            <para><emphasis role="bold">Info</emphasis></para>
            <itemizedlist>
                    <listitem><para><emphasis>User manual - </emphasis>Open a window with this manual :)</para></listitem>
                    <listitem><para><emphasis>About - </emphasis>The usual window with licence information, acknowledgements, etc.</para></listitem>
            </itemizedlist>

        
        
        
        
        </section>
        
        <section id="sect.main_toolbar">
                <title>The main toolbar</title>
                <para>Before analyzing the two main frames of Hydrogen, let's take a quick look at the main toolbar and its components:</para>
                
                <itemizedlist>
                    <listitem><para>Pilot the song using the start, stop, pause, etc. buttons</para></listitem>
                    <listitem><para>Choose between "pattern" or "song" mode: in "pattern" mode only the currently selected pattern will play, while in "song" mode all patterns inserted will be played.</para></listitem>
                    <listitem><para>An advanced tap tempo function: choose note length and how many notes to wait before recalculating BPM, then click the comma key repeatedly until the 'R' letter will appear and the BPM will be updated.  (see <xref linkend="sect.tap_tempo"/>)</para></listitem>
                    <listitem><para>Manually set BPM</para></listitem>
                    <listitem><para>Manage JACK transport</para></listitem>
                    <listitem><para>Open the mixer and the instrument rack panels</para></listitem>
                </itemizedlist>
        
        
                <figure id="fig.main_toolbar">
                <title>The Main Toolbar</title>
                <mediaobject>
                        <imageobject>
                                
                                <imagedata fileref="img/MainToolbar.png" format="PNG"/>
                                
                        </imageobject>
                </mediaobject>
                </figure>

                <itemizedlist mark="opencircle">
                        <listitem><para><inlinemediaobject><imageobject>
                                <imagedata fileref="img/background_Control.png" format="PNG"/>
                        </imageobject></inlinemediaobject>
                                </para><para>Main controls to start <emphasis role="bold">[Hotkey = Spacebar]</emphasis>, stop, fast forward, rewind, loop a song or a pattern.</para>
                        </listitem>
                        
                        <listitem><para><inlinemediaobject><imageobject>
                                <imagedata fileref="img/background_Mode.png" format="PNG"/>
                        </imageobject></inlinemediaobject></para><para>Set Pattern/Song Mode.</para></listitem>
        
                        <listitem><para><inlinemediaobject><imageobject>
                                <imagedata fileref="img/background_BPM.png" format="PNG"/>
                        </imageobject></inlinemediaobject></para><para>Set speed of playing (range: 30-400 bpm) <emphasis role="bold">[Hotkey = mouse wheel]</emphasis> and button to enable/disable metronome</para></listitem>

                        <listitem><para><inlinemediaobject><imageobject>
                                <imagedata fileref="img/cpuload.png" format="PNG"/>
                        </imageobject></inlinemediaobject></para><para>Shows CPU load.</para></listitem>

                        <listitem><para><inlinemediaobject><imageobject>
                                <imagedata fileref="img/midi_in.png" format="PNG"/>
                        </imageobject></inlinemediaobject></para><para>Shows MIDI events.</para></listitem>

                        <listitem><para><inlinemediaobject><imageobject>
                                <imagedata fileref="img/jack_transport.png" format="PNG"/>
                        </imageobject></inlinemediaobject></para><para>Click to enable Jack transport: Hydrogen will work as 'slave' with another 'master' program (e.g. Ardour). This applet is only available if Jack Audio Driver is selected.</para></listitem>
                </itemizedlist>

        <para>Other useful keybindings (not customizable for the moment):</para>
                
        <itemizedlist mark="opencircle">
                <listitem>
                        <para>
                        <emphasis role="bold">[CTRL + O]</emphasis> = Open File
                        </para>
                </listitem>
                <listitem>
                        <para>
                        <emphasis role="bold">[CTRL + S]</emphasis> = Save File
                        </para>
                </listitem>
                <listitem>
                        <para>
                        <emphasis role="bold">[Backspace]</emphasis> = Restart song or pattern from the beginning
                        </para>
                </listitem>
                </itemizedlist>

                <section id="sect.tap_tempo">
                        <title>Tap Tempo and BeatCounter</title>

                        <para>It is possible to change tempo at any time using
                        the tap-tempo and BeatCounter features of Hydrogen.  You
                        can change these while playing or while the song is
                        stopped.  To change the tempo, hit
                        the <keycap>,</keycap> (comma) key in tempo for the
                        number of beats in the measure.  After the correct
                        number of beats are met, the tempo will change to the
                        average tempo that you tapped in.  If you continue to
                        tap, these new taps will become a part of a rolling
                        average.  If you tap accidentally, or if you wait too
                        long between taps, the tap tempo counter will start
                        over.</para>

                        <para>The Tap Tempo is a part of the BeatCounter, which
                        is essentially a Tap Tempo on steroids.  By default the
                        BeatCounter display is not visible.  To see the
                        BeatCounter widget click the upright button
                        (<guilabel>BC</guilabel>) between Song/Pattern mode
                        selector and the BPM-widget.  Or, it can be shown by
                        pressing the comma key (<keycap>,</keycap>).</para>

                        <para>The tempo that you tap will be considered even
                        beats of the beat type.  The beat type can be set to 1/8
                        (for eight-note beats), 1/4 (for quarter-note beats),
                        1/2 (for half-note beats), and 1/1 (for whole-note
                        beats).  To change the beat type use the left arrow
                        buttons.  To change the number of beats that are
                        counted, use the right arrow button.  You can set from 2
                        to 16 beats.  (I.e. if you set the beat to 6, you will
                        have to tap 6 times before the new tempo is computed and
                        set.)  When the display shows an <guilabel>R</guilabel>,
                        it means that the BeatCounter is ready to start from 0.
                        Every time you tap with the comma key, it will show the
                        number of taps that you have entered (1, 2,
                        3...).</para>

                        <para>The button in the bottom right-hand controls the
                        auto-start feature, and it toggles
                        between <guilabel>S</guilabel>
                        and <guilabel>P</guilabel>.  When it
                        shows <guilabel>P</guilabel> for
                        (<emphasis>Play</emphasis>), the song will set the new
                        tempo and automatically start to play after you tap the
                        right number of beats (if it's not already playing, of
                        course).  This way, if you have the BeatCounter set up
                        for 4/4, you can tap 1-2-3-4, and start playing on the
                        next beat.  When it shows <guilabel>S</guilabel>
                        (for <emphasis>Set BPM</emphasis>), the auto-start is
                        disabled.</para>

                        <para>For example: Suppose you have a live band,
                        Hydrogen, and a softsynth that is controlled by
                        Seq24)... and you want them all to start at the same
                        time.  Set the beat type to 1/4 and the number of beats
                        to 4.  Enable auto-start (button
                        shows <guilabel>P</guilabel>).  Count off the band
                        1-2-3-4 (while tapping the comma key) &mdash; and
                        everyone starts on 1.</para>

                        <para>Another example: Same situation, but the song
                        doesn't require Hydrogen or synths until some point
                        later.  During that time, a human (e.g. guitar player)
                        will be setting the tempo.  On the measure before
                        Hydrogen is supposed to play, tap the comma key 1-2-3-4
                        with the beat... and you're in on the next beat (at the
                        right tempo).</para>

                        <para>If you are using the JACK Transport, the
                        BeatCounter continues to work.  If another program is
                        the JACK Transport Master, Hydrogen will respond to
                        tempo change events from that application.  Note that in
                        this situation, Hydrogen is supposed to be
                        a <emphasis>slave</emphasis>, so some of the BeatCounter
                        features will be disabled or will not work properly.  If
                        Hydrogen is the JACK Transport Master, tempo changes
                        from Hydrogen will be reflected in those programs (if
                        they support it).</para>

                        <para>Some of the settings to adjust the BeatCounter's
                        latency compensation, and they are located on the
                        <guilabel>General</guilabel> tab of the Preferences
                        Dialog (

                        <menuchoice>
                                <guimenu>Tools</guimenu>
                                <guimenuitem>Preferences</guimenuitem>
                        </menuchoice>

                        ). Here there are two spinboxes:</para>

                        <itemizedlist>
                                <listitem><para><emphasis role="bold"><guilabel>Beat
                                counter drift compensation in
                                1/10ms</guilabel></emphasis> &mdash; adjust to
                                compensate for latency between the keyboard and
                                the program.</para></listitem>

                                <listitem><para><emphasis role="bold"><guilabel>Beat
                                counter start offset in ms</guilabel></emphasis>
                                &mdash; adjust the time between the
                                BeatCounter's last input stroke and when the
                                song starts playing (if auto-start is
                                activated).</para></listitem>
                        </itemizedlist>

                        <para>Note that these can be set to positive (+) or
                        negative (-) values.  In order to find useful values for
                        these, you will need to take some time to play with it.
                        Also, you may want different values depending on the
                        speed of your hardware, audio devices, drivers, etc.
                        Using the BeatCounter effectively requires
                        practice.</para>

                </section>

        </section>
        
        <section id="sect.song_editor">
                <title>Song Editor</title>

                <para>
                The "Song Editor" (<xref linkend="fig.song_editor"/>) gives an overview of the whole timeline of the song (e.g. intro, verse, bridge, chorus and so on); each blue coloured square on this panel is a complete bar as shown in the underlying "Pattern Editor" panel. Here we have complete freedom to add, remove or move patterns in any order we prefer. We can also copy and paste patterns: use left mouse button to highlight an area and drag it around. Dragging with CTRL key pressed copies the patterns.
                </para>

                <para>
                The Song Editor comes with 7 buttons:
                </para>
                <para>
                        <inlinemediaobject>
                                <imageobject>
                                        <imagedata fileref="img/bg_topPanel.png" format="PNG"/>
                                </imageobject>
                        </inlinemediaobject>
                </para>

<itemizedlist mark="opencircle">

                <listitem>
                <para><inlinemediaobject><imageobject>
                        <imagedata fileref="img/btn_clear_off.png" format="PNG"/>
                </imageobject></inlinemediaobject> Completely delete all patterns (asks for confirmation!).
                </para>
                </listitem>

                <listitem>
                <para><inlinemediaobject><imageobject>
                        <imagedata fileref="img/btn_new_on.png" format="PNG" />
                </imageobject></inlinemediaobject> Create a new pattern (and asks for a name).
                </para>
                </listitem>

                <listitem>
                <para><inlinemediaobject><imageobject>
                        <imagedata fileref="img/btn_updown.png" format="PNG" />
                </imageobject></inlinemediaobject> Move currently selected pattern up or down.
                </para>
                </listitem>



                <listitem>
                <para><inlinemediaobject><imageobject>
                        <imagedata fileref="img/btn_select.png" format="PNG"/>
                </imageobject></inlinemediaobject> Enable selecting patterns for copy &amp; paste (Select Mode).
                </para>
                </listitem>

                <listitem>
                <para><inlinemediaobject><imageobject>
                        <imagedata fileref="img/btn_draw.png" format="PNG"/>
                </imageobject></inlinemediaobject> Enable Draw Mode.
                </para>
                </listitem>
                
                <listitem>
                <para><inlinemediaobject><imageobject>
                        <imagedata fileref="img/btn_pattern_mode.png" format="PNG"/>
                </imageobject></inlinemediaobject> Switch from "Single pattern mode" to "Stacked pattern mode" and back..
                </para>
                </listitem>
</itemizedlist>
 
        <para>
        Under these buttons there is a list of patterns created and when they will played (each square == 1 bar). Click
        on an squarebox to add or cancel the pattern. Clicking on right mouse button over the name of a pattern will bring up a menu to change name of the pattern or to allow copying/deleting it. Patterns with very same name are not allowed.
        </para>

        <figure id="fig.song_editor">
        <title>The Song Editor</title>
        <mediaobject>
                <imageobject>
                        <imagedata fileref="img/SongEditor.png" format="PNG" />
                </imageobject>
        </mediaobject>
        </figure>

        </section>

        <section id="sect.pattern_editor">
                <title>Pattern Editor</title>
                <para>
                The "Pattern Editor" frame (<xref linkend="fig.pattern_editor"/>) lets us create or modify the pattern (bar) which is being played, or add/remove notes and tune intensity as well. On the higher-left side you find a pair of LCD screens: the first one lets you choose the size of a pattern while the second represents the current grid resolution (4 through 64). 
                
                Selecting an instrument which has at least one note in the pattern will show a few vertical bars (one per note) on the lowest part of this frame. Those frame shows the so called "note properties". This are special properties which can be set for every
                single note. Hydrogen knows of 3 Properties: Velocity, Pan and Lead/Lag. Lead and Lag allows a slight note lead or lag in respect of the actual beat. The range is ca. 5 ticks which equals around ca. 10 ms at a tempo of 120bpm.
                </para>

                <para>
                The button
                <inlinemediaobject>
                        <imageobject>
                                <imagedata fileref="img/btn_hear_on.png" format="PNG" />
                        </imageobject>
                </inlinemediaobject>

                (hear new notes) will play the sample as it's been added to the pattern. Finally you can move an instrument up and down in the sequence with the buttons
                
                <inlinemediaobject>
                        <imageobject>
                                <imagedata fileref="img/btn_updown.png" format="PNG" />
                        </imageobject>
                </inlinemediaobject>

. A useful <quote>Quantize</quote> feature is available activating
        
                <inlinemediaobject>
                        <imageobject>
                                <imagedata fileref="img/btn_quant_off.png" format="PNG"/>
                        </imageobject>
                </inlinemediaobject>
        
        . This way the beats inserted will automatically respect the grid resolution currently applied.
                </para>

                <figure id="fig.pattern_editor">
                  <title>The Pattern Editor</title>
                        <mediaobject>
                                <imageobject>
                                        <imagedata fileref="img/PatternEditor.png" format="PNG" />
                                </imageobject>
                        </mediaobject>
                </figure>

                <para>
                Rememeber this constraint concerning the grid: if you are working with a resolution of 16 you can't go back to 8 and remove a 16th note; on the other hand if you are working with a resolution of 8 and you try to insert a note in the middle of two bars (looking for a 16 bars precision), notes will be placed in the previous or in the following 8th bar.
This contraint can be removed if you disable the whole grid resolution (choose "off" from the grid resolution LCD control). Now you'll be able to place notes wherever you prefer.
                </para>
                
                <para>
                Each instrument has its own set of features accessible right-clicking with your mouse on it;  <quote><emphasis role="bold">Fill/Clear notes</emphasis></quote> fills or deletes every note of that instrument in the current pattern (remember that filling a pattern is always relative to the grid resolution set) and finally <quote><emphasis role="bold">Randomize velocity</emphasis></quote> automatically apply a pseudo-random velocity to each note of that instrument in the pattern. The more velocity you set on the instrument, the more hydrogen will hit <quote>hard</quote> on that instrument when played.
                </para>
            
                <para>
                    The small green and red squares beside the instrument name are the <quote><emphasis role="bold">mute</emphasis></quote> and <quote><emphasis role="bold">solo</emphasis></quote> buttons.
                </para>
                
                <informalfigure id="ifig.pattern_editor_instrument">
                <mediaobject>
                        <imageobject>
                                <imagedata fileref="img/PatternEditorInstr.png" format="PNG" />
                        </imageobject>
                </mediaobject>
                </informalfigure>

                <para>Also, you can set new beats clicking on
                
                <inlinemediaobject>
                        <imageobject>
                                <imagedata fileref="img/btn_record_over.png" format="PNG"/>
                        </imageobject>
                </inlinemediaobject>
                
                which enables direct input by MIDI events or by keyboard according to the following map key=instrument:</para>
                
                <para><emphasis>Note that the name of the instrument depends on the drumkit loaded. This list refers to the GMKit loaded by default. The position of the instrument, however, is the same.</emphasis></para>
                
                <itemizedlist>
                <listitem><para>Z = Kick</para></listitem>
                <listitem><para>X = Snare Jazz</para></listitem>
                <listitem><para>C = Snare Rock</para></listitem>
                <listitem><para>V = Tom Low</para></listitem>
                <listitem><para>B = Tom Mid</para></listitem>           
                <listitem><para>N = Tom Hi</para></listitem>
                <listitem><para>M = Cowbell</para></listitem>           
                <listitem><para>Q = Ride Jazz</para></listitem>
                <listitem><para>W = Ride Rock</para></listitem>         
                <listitem><para>E = Instrument No. 17 (currently not assigned)</para></listitem>
                <listitem><para>R = Instrument No. 18 (currently not assigned)</para></listitem>                
                <listitem><para>T = Instrument No. 20 (currently not assigned)</para></listitem>
                <listitem><para>Y = Instrument No. 22 (currently not assigned)</para></listitem>                
                <listitem><para>U = Instrument No. 24 (currently not assigned)</para></listitem>
                <listitem><para>S = Stick</para></listitem>             
                <listitem><para>D = Hand Clap</para></listitem>
                <listitem><para>G = Closed HH</para></listitem>         
                <listitem><para>H = Pedal HH</para></listitem>
                <listitem><para>J = Open HH</para></listitem>           
                <listitem><para>2 = Crash</para></listitem>
                <listitem><para>3 = Crash Jazz</para></listitem>                
                <listitem><para>5 = Instrument No. 19 (currently not assigned)</para></listitem>
                <listitem><para>6 = Instrument No. 21 (currently not assigned)</para></listitem>                
                <listitem><para>7 = Instrument No. 23 (currently not assigned)</para></listitem>
                </itemizedlist>

        
        <para>Here's a quick reference of the above bindings for your convenience. See <xref linkend="chap.create_song"/> for a basic walkthrough of how the pattern editor works.</para>
        
        <informalfigure id="ifig.letters_keyboard">
        <mediaobject>
                <imageobject>
                        <imagedata fileref="img/tastiera.png" format="PNG" />
                </imageobject>
        </mediaobject>
        </informalfigure>
        
        </section>

        <section id="sect.mixer">
                <title>Mixer</title>
                
                <figure id="fig.mixer">
                <title>The Mixer</title>
                <mediaobject>
                        <imageobject>
                                <imagedata fileref="img/Mixer.png" format="PNG" />
                        </imageobject>
                </mediaobject>
                </figure>

<para>The Mixer frame (<xref linkend="fig.mixer"/>) is useful for tuning a global or single volume of the current drumkit. It shows the current peak (click on 

        <inlinemediaobject>
                <imageobject>
                        <imagedata fileref="img/showPeaks_on.png" format="PNG" />
                </imageobject>
        </inlinemediaobject>    

         to disable, useful on old CPUs) and let you set the maximum peak allowed (tune with the fader knob of the instrument), lets you modify attributes like pan, play solo 
        
        <inlinemediaobject>
                <imageobject>
                        <imagedata fileref="img/btn_solo_on.png" format="PNG" />
                </imageobject>
        </inlinemediaobject>
        
        , mute 
        
        <inlinemediaobject>
                <imageobject>
                        <imagedata fileref="img/btn_mute_on.png" format="PNG" />
                </imageobject>
        </inlinemediaobject>
        
        or test play only that instrument

        <inlinemediaobject>
                <imageobject>
                        <imagedata fileref="img/btn_play_on_mixer.png" format="PNG" />
                </imageobject>
        </inlinemediaobject>

        ; selecting in the Pattern Editor an instrument causes a blue LED to light on (near the play button). Near the global volume knob, you can set 3 global effect such a swing (shifts a few notes back or forward not randomly), timing (modify timings of the notes) and humanize effect (random velocity editing).
        </para>

        <para>
                In addition to all this you can set up to 4 special LADSPA effects for each instrument switching the
                
        <inlinemediaobject>
                <imageobject>
                        <imagedata fileref="img/showFX_on.png" format="PNG" />
                </imageobject>
        </inlinemediaobject>
        
        button. See next section for a detailed overview.
        
        <informalfigure id="ifig.mixer_fx">
                <mediaobject>
                        <imageobject>
                                <imagedata fileref="img/MixerFX.png" format="PNG" />
                        </imageobject>
                </mediaobject>  
        </informalfigure>

        </para>

        </section>

        <section id="sect.sound_library">
          <title>Sound Library (Drumkit Manager)</title>

          <para>The Sound Library saves you time in managing your drum kits,
          favorite patterns, and favorite songs.  When making new songs and drum
          kits, the Sound Library makes it easier for you to reuse and mix the
          instruments and patterns from other kits and songs.</para>

          <section id="sect.systemdrumkits">
            <title>System Drumkits</title>

            <para>This lists the drumkits that were installed by your system
            administrator.  It was determined by the compile-time prefix.  On
            Unix-like operating systems, this is
            usually <filename role="directory">/usr/share/hydrogen/data/drumkits</filename>,
            or
            possibly <filename role="directory">/usr/local/share/hydrogen/data/drumkits</filename>.
            These kits are available to all users on the system, and users are
            usually not able to add to them.</para>

            <para>To load a drumkit from here, right-click the drumkit and
            select <guimenuitem>Load</guimenuitem>.  This will replace your
            current drumkit with the one that you selected.  To load a single
            instrument from that kit, left-click the <guibutton>plus</guibutton>
            to the left of the drumkit's name to show all the instruments.  With
            your left mouse button, click and drag the instrument into your
            current kit.  The instrument will be added to the drumkit that you
            currently have loaded.</para>
          </section>

          <section id="sect.userdrumkits">
            <title>User Drumkits</title>

            <para>These are your own drum kits that you can manage yourself.
            They are usually stored
            in <filename role="directory">$HOME/.hydrogen/data/drumkits</filename>.
            When you are creating a new drumkit, you can save it here by
            selecting <menuchoice><guimenu>Instruments</guimenu><guimenuitem>Save
            library</guimenuitem></menuchoice>.</para>


            <para>Loading drumkits and instruments to use is the same as for the
            System Drumkits (see <xref linkend="sect.systemdrumkits"/>).</para>

          </section>
          <section id="sect.sl.patterns">
            <title>Patterns in the Sound Library</title>

            <para>Before you save your favorite patterns to the sound library,
            be sure to edit it's properties by right-clicking and
            selecting <guimenuitem>Properties</guimenuitem>.  There, you can
            give the pattern a title and a category.  You can use one of the
            categories already provided, or create your own categories by simply
            typing in a category name.  The category name is important, because
            the patterns will be filed by category in the Sound Library.</para>

            <para>You can save your favorite patterns in the sound library by
            right clicking the title of the pattern in the song editor, and
            selecting <guimenuitem>Save Pattern</guimenuitem>.  It will appear
            in the Sound Library underneath <guilabel>Patterns</guilabel> and
            the category that you assigned to the pattern.</para>

          </section>
          <section id="sect.sl.songs">
            <title>Songs in the Sound Library</title>

            <para>To save songs in the Sound Library, put them in your data
            directory underneath the <filename role="directory">songs</filename>
            folder
            (usually <filename role="directory">$HOME/data/songs</filename>.  To
            remove them, remove the file from that folder.</para>
          </section>

        </section>
        <section id="sect.instrument_editing">
                <title>Drumkits and Instrument Editing</title>

                <para>Creating a new drumkit with Hydrogen is done with the
                Instrument Editor.  Using the instrument editor you can load
                samples, set envelope parameters, set the gain, and a few other
                advanced features like mute groups, low-pass resonance filter,
                and pitch randomization.</para>

                <para>Instead of creating your own drumkit, you can also use or
                download existing drumkits using
                the <xref linkend="sect.sound_library"/>.</para>

                <!-- Need to add an explaination of what the instrument list
                     and instrument editor are. -->

        <section id="sect.instrument_editing.concepts">
                <title>Concepts</title>

                <para>
                  The synthesizer in Hydrogen is a sample-based synthesizer.  A
                  sample is a piece of pre-recorded audio (usually between .1
                  sec and 3 sec).  To play a note, the sample is simply played
                  back at the right time.  There's a few concepts and terms that
                  you should understand when you are putting together a drumkit.
                  (See <xref linkend="glossary"/> for more
                  detailed explanations.)
                </para>

                <variablelist>
                  <title>Sampling Synthesizer Terms</title>
                  <varlistentry>
                    <term>Sample</term><listitem><para>A short recording of a
                    sound, typically between .1 and 3.0 seconds
                    long.</para></listitem>
                  </varlistentry>
                  <varlistentry>
                    <term>Gain</term><listitem><para>Volume
                    adjustment.</para></listitem>
                  </varlistentry>
                  <varlistentry>
                    <term>Velocity</term><listitem><para>How hard you hit a
                    note.</para></listitem>
                  </varlistentry>
                  <varlistentry>
                    <term>ADSR Envelope Generator</term><listitem><para>An
                    Attack/Decay/Sustain/Release envelope generator.  After you
                    trigger a note, Hydrogen
                    will <emphasis>attack</emphasis> the note by
                    increasing its volume from 0 to the full velocity of the
                    note.  After reaching full velocity, it
                    will <emphasis>decay</emphasis> the note by
                    lowering the volume until it reaches
                    the <emphasis>sustain</emphasis> level.  When
                    the note is <emphasis>released</emphasis>,
                    Hydrogen reduces the volume from the sustain level back down
                    to 0.</para></listitem>
                  </varlistentry>
                  <varlistentry>
                    <term>Attack</term><listitem><para>The amount
                    of <emphasis role="bold">time</emphasis> to go from 0 to
                    full velocity.</para></listitem>
                  </varlistentry>
                  <varlistentry>
                    <term>Decay</term><listitem><para>The amount
                    of <emphasis role="bold">time</emphasis> to go from full
                    velocity to the sustain volume.</para></listitem>
                  </varlistentry>
                  <varlistentry>
                    <term>Sustain</term><listitem><para>The <emphasis role="bold">level</emphasis>
                    (how loud) to hold the note between the sustain and the
                    release.  It is a percentage of the velocity.  It does not
                    depend on time.</para></listitem>
                  </varlistentry>
                  <varlistentry>
                    <term>Release</term><listitem><para>The amount
                    of <emphasis role="bold">time</emphasis> to go from the
                    sustain volume back down to 0.</para></listitem>
                  </varlistentry>
                </variablelist>

                <para>
                  Typical samples that are used in Hydrogen are: the sound of a
                  single drum hit, the sound of a single cymbal hit, the sound
                  of a single cowbell hit.  Whenever you put a note in the
                  pattern (or play a note using MIDI), Hydrogen will play
                  whatever sound you have loaded.  So, to put together a drum
                  kit you need to gather short recordings of the bass drum, each
                  tom, each cymbal, the high hat open, the high hat closed, the
                  snare drum (snare on), the snare drum (snare off), rim shots,
                  etc.
                </para>

                <para>
                  However, there are no rules about what a sample can be.  It's
                  not uncommon to use Hydrogen to trigger non-drum sounds like:
                  audio clips of people talking, a clip from a song, sound
                  effects, audio clips from movies, and famous people speaking.
                  Be creative!
                </para>

        </section>
        <section id="sect.instrument_editing.new_kit">
                <title>Creating a New Drumkit</title>

                <para>To start a brand new drum kit, select
                  <menuchoice>
                    <guimenu>Instruments</guimenu>
                    <guimenuitem>Clear All</guimenuitem>
                  </menuchoice>.
                  This will give you a bank of 32 blank instruments.  To delete
                  instruments, right-click on on each instrument and select
                  <guimenuitem>Delete Instrument</guimenuitem>.  To add
                  more instruments, select
                  <menuchoice>
                    <guimenu>Instruments</guimenu>
                    <guimenuitem>Add instrument</guimenuitem>
                  </menuchoice>.
                </para>

                <para>Select an instrument to start editing it.  This
                is done by left-clicking on the name of the instrument in the
                instrument list (at the left).  You will notice that the name of
                the instrument in the Instrument Editor matches the one that you
                clicked.</para>

                <para>After you have your drum kit working the way you
                want, select
                  <menuchoice>
                    <guimenuitem>Instruments</guimenuitem>
                    <guimenuitem>Save library</guimenuitem>
                  </menuchoice>.  It will ask you for the name of the
                  kit to save.  If you wish
                  to <emphasis>overwrite</emphasis> an existing kit,
                  you will need to type in the same name as the kit
                  that you want to replace.</para>

                <para>Drumkits are automatically stored in
                the <filename class="directory">data</filename>
                directory
                (i.e. <filename class="directory">$HOME/data/drumkits</filename>).</para>

                <para>To export a drumkit (for sharing with others),
                it must first be loaded into your Sound Library.
                Then, select
                  <menuchoice>
                    <guimenuitem>Instruments</guimenuitem>
                    <guimenuitem>Export library</guimenuitem>
                  </menuchoice>
                from the menu.  Select the drum kit that you wish to
                export, and give it a file name to save it to.</para>

        </section>
        <section id="sect.instrument_editing.new_instrument">
                <title>Creating an Instrument and Layers</title>

                <para>For each instrument in a drum kit, you can load
                several samples and set different synthesizer
                parameters.  This section will step you through how to
                create a new instrument and load the samples.</para>

                <para>To begin creating an instrument, select
                  <menuchoice>
                    <guimenu>Instruments</guimenu>
                    <guimenuitem>Add instrument</guimenuitem>
                  </menuchoice>.  This will give you a blank
                  instrument to start from.</para>

                <para>Now, you need two samples.  Any .WAV or .FLAC file will
                do.  Hydrogen provides several in
                the <filename class="directory">data/drumkits</filename>
                directory.</para>

                <para>In the instrument editor, click
                on <guibutton>Layers</guibutton>.  You can layer several samples
                into the instrument.  Which one is played depends on the
                velocity of the incoming note.  Click <guibutton>Load
                Layer</guibutton> and point the <guimenu>Audio File
                Browser</guimenu> to your sample.  Note that the <guimenu>Audio
                File Browser</guimenu> will allow you to preview the sample
                before you load it.  It will also allow you to load more than
                one sample at a time.  But for now, only load one.</para>

                <para>After you load the sample, you'll see that there
                is now a <guilabel>1</guilabel> at the top, and the
                topmost rectangle has turned light blue.  To load a
                second sample, click the slot just below it, and then
                click <guibutton>Load Layer</guibutton> to bring in
                another sample.</para>

                <para>After bringing in both samples, you'll probably
                notice that only the <emphasis>first</emphasis> sample
                is being played whenever you trigger the instrument.
                This is because you need to set
                the <emphasis>velocity</emphasis> ranges for the
                layers.  Move your mouse to the sides of the light
                blue rectangles and you see that you get a left-right
                drag cursor.  Now drag the sample to the left or right
                (like a curtain).  You will now see Layer 2
                appear.</para>

                <para>The velocity setting for the layer is 0-velocity
                on the left, and full velocity on the right.  Set up
                Layer 1 to sound for soft notes, and Layer 2 to sound
                for hard notes.  (I.e. Layer 1 on the left and Layer 2
                on the right.)</para>

                <para>Now, in the pattern area, set up a simple
                pattern that plays this instrument.  Adjust the
                velocity settings on each note so that you can get the
                different samples to sound.  Now set the pattern to
                loop and notice how your different samples are getting
                triggered.  (To learn about editing a pattern,
                see <xref linkend="sect.pattern_editor"/>)</para>

                <para>For each layer, you can set
                the <guibutton>Gain</guibutton> and
                the <guibutton>Pitch</guibutton>.  The pitch also has
                a <guibutton>Fine</guibutton> adjustment.</para>

                <para>Use the <guibutton>Gain</guibutton> adjustment
                to control how loud the sample will play.  This is
                necessary because it's extremely difficult to get a
                set of samples that all sound at about the same
                volume.  By adjusting here, the samples that were
                recorded too quietly can be turned up to match your
                loud samples (that had to be turned down).</para>

                <warning>
                  <para>It is very easy to set
                  the <guibutton>Gain</guibutton> too high, causing
                  your sample to clip.  Remember to test the gain with
                  full-velocity notes.  If you clip your signal here,
                  it will only get worse as Hydrogen processes
                  it.</para>
                </warning>

                <para>The pitch of the sample can be modified with the
                pitch controls.  The <guibutton>Pitch</guibutton> knob
                adjust the pitch in musical half-steps.  (So, -12 is
                down 1 octave).  The pitch on the right adjusts the
                pitch &plusmn;50 cents.  (One half-step is 100
                cents.)</para>

                <note>
                  <para>The pitch is adjusted by playing the sample
                  back faster or slower.  This is called the Dopplar
                  Effect.  So, if you have a 1-second sample that you
                  turn down -12 (1 octave), you sample will only last
                  for .5-seconds.</para>
                </note>
        </section>
        <section id="sect.instrument_editing.parameters">
                <title>Instrument Parameters</title>

                <para>In the instrument editor, click on
                the <guibutton>General</guibutton> button.  Here you
                can adjust several parameters that are for the whole
                instrument (not for each layer).  The parameters that
                you can adjust are:</para>

                <itemizedlist>
                  <listitem>
                    <para><emphasis role="bold">Envelope
                    parameters</emphasis>: <guibutton>Attack</guibutton>, <guibutton>Decay</guibutton>,
                    <guibutton>Sustain</guibutton>, <guibutton>Release</guibutton>.  (See
                    <xref linkend="def.envelopegenerator"/>)</para>
                  </listitem>
                  <listitem>
                    <para><emphasis role="bold"><guibutton>Gain</guibutton></emphasis>:
                    The overall volume of the instrument.</para>
                  </listitem>
                  <listitem>
                    <para><emphasis role="bold"><guibutton>Mute
                    Group</guibutton></emphasis>: Which mute group
                    this instrument is a member of (see
                    <xref linkend="def.mutegroup"/>).</para>
                  </listitem>
                  <listitem>
                    <para><emphasis role="bold">Filter
                    Parameters</emphasis>: <guibutton>Byp</guibutton>ass, <guibutton>Cutoff</guibutton>,
                      <guibutton>Resonance</guibutton>.</para>
                  </listitem>
                  <listitem>
                    <para><emphasis role="bold"><guibutton>Random
                    Pitch</guibutton></emphasis></para>
                  </listitem>
                </itemizedlist>

                <para>It's important that you
                understand <xref linkend="sect.instrument_editing.concepts"/>
                in order to continue on.</para>

                <section id="sect.instrument_editing.envelope_parameters">
                  <title>Envelope Parameters</title>

                  <para>When the instrument is triggered, its volume
                  is run through an ADSR Envelope.  The parameters
                  operate as follows:</para>

                  <itemizedlist>
                    <listitem>
                      <para><emphasis role="bold">Attack</emphasis>
                      &mdash; the amount of <emphasis>time</emphasis>
                      that the volume of the sample goes from 0 to the
                      full velocity of the note.  If the value is 0,
                      the sample will play immediately at full
                      velocity.  If the value is 1.0, the sample
                      volume will use the maximum time available for
                      the attack paramater.
                        <footnote id="fn.adsrtimes">
                          <para>The attack, decay, and release parameters are
                          all set by the number of <emphasis>audio
                          samples</emphasis>.  This means that the time changes
                          depending on the sample rate of your sound card.  The
                          max time for each of them is 100,000 audio samples
                          (typ. 2.27 sec at 44.1 kHz).</para>
                        </footnote>
                      </para>
                    </listitem>
                    <listitem>
                      <para><emphasis role="bold">Decay</emphasis>
                      &mdash; the amount of <emphasis>time</emphasis>
                      for the volume of the sample to go from full
                      velocity down to the sustain volume.  If the
                      value is 0, the sample will immediately skip
                      from the attack volume to the sustain volume.
                      If the value is 1.0, the sample volume will use
                      the maximum time available for the decay
                      parameter.<footnoteref linkend="fn.adsrtimes"/></para>
                    </listitem>
                    <listitem>
                      <para><emphasis role="bold">Sustain</emphasis>
                      &mdash; the <emphasis>volume</emphasis> to play
                      the note after the decay phase is over, and
                      until the note is released.  If set to 0, the
                      note will be silent.  If set to 1.0, the note
                      will play at full velocity.</para>
                    </listitem>
                    <listitem>
                      <para><emphasis role="bold">Release</emphasis> &mdash;
                      the <emphasis>time</emphasis> to fade out the note from
                      the sustain volume back down to 0 (silent).  If set to 0,
                      the note will fade out in the minimum amount of time
                      (about 5 ms).  If set to 1, it will fade out for
                      the maximum time
                      available.<footnoteref linkend="fn.adsrtimes"/></para>
                    </listitem>
                  </itemizedlist>

                  <para>If the sample is shorter than the times that
                  you specify, the sample will end, regardless of
                  which phase of the ADSR it is in.  If the note is
                  sustained, it does <emphasis>not</emphasis> draw out
                  the note while you are holding it.  It only holds
                  the gain (volume) parameter during that time.</para>

                </section>

                <section id="sect.instrument_editing.gain_and_mute_group">
                  <title>Gain and Mute Group</title>

                  <para>The gain sets the overall volume for the
                  sample.  This gain is applied after the gain that
                  you set for the layer, and before the gain that is
                  set for the mixer.  If the Gain is 0, the instrument
                  will be silent.  If the gain is 1.0 the volume of
                  the samples will not be adjusted (i.e. 0 dB).  If
                  the gain is set higher, the samples will be
                  amplified.</para>

                  <warning>
                    <para>It is very easy to set
                      the <guibutton>Gain</guibutton> too high, causing
                      your sample to clip.  Remember to test the gain with
                      full-velocity notes.  If you clip your signal here,
                      it will only get worse as Hydrogen processes
                      it.</para>
                  </warning>

                  <para>Hydrogen provides more mute groups than you
                  know what to do with (over 256).  A mute group is a
                  grouping of instruments that are mutually exclusive
                  &mdash; only one instrument may be playing at any
                  time.  If one is playing and another instrument in
                  the group is triggered, it will immediately silence
                  (mute) and start playing the other instrument.  This
                  is useful, especially, for instruments like hi-hats
                  where the open sound and the closed sound are
                  different instruments.</para>

                  <para>If the mute group is set
                  to <guilabel>Off</guilabel>, then the instrument is
                  not part of any mute grouping.  If the mute group is
                  set to any number, then that is the group that the
                  instrument is a part of.  To set other instruments
                  into the same grouping, set their mute group
                  parameter to the same number.  (For example, to
                  group all the high-hat instruments, you can set all
                  their mute group parameters to 1.  To have a snare
                  drum mute group, set their mute group parameters to
                  2.)</para>

                </section>

                <section id="sect.instrument_editing.filter_and_random_pitch">
                  <title>Filter and Random Pitch</title>

                  <para>The filter is a low-pass resonance filter.  If you don't
                  wish to use is, click the <guibutton>BYP</guibutton>ass button
                  so that it's red.  If it's not red, then the filter is active.
                  The cutoff parameter adjusts the cutoff frequency for the
                  filter.  The resonance parameter adjusts how much to resonate
                  the cutoff frequency.  If the resonance is set to 0, then the
                  filter is just a simple low-pass filter.</para>

                  <note>
                    <para>The cutoff frequency of the filter varies with the
                    sample rate of your audio card.  The range of the knob (0 to
                    1.0) is optimized for a 48,000 kHz sample rate.</para>
                    <!-- NOTE:  I tried to reverse engineer the LPRF in the
                         sampler to calculate what the cutoff frequency is.
                         I think it's *something* kind of like this:

                         f = cutoff * samplerate / 2

                            - OR MAYBE -

                         f = sqrt(cutoff) * samplerate / 2   (or / 4)

                         http://en.wikipedia.org/wiki/Low-pass_filter                         
                         -gabriel
                         -->
                  </note>

                  <para>The random pitch paramater allows you to randomly vary
                  the pitch of the sample every time it is triggered.  The value
                  is set between 0 and 1.0.  The pitch change is fairly small:
                  &plusmn;2 half-steps &times; value.  Using this sparingly can
                  help your sequences to sound more like a real drummer.</para>
                
                </section>
        </section>
        <section id="sect.instrument_editing.tips">
                <title>Tips on Editing Instruments</title>

                <para>With all of the different parameters available to tweak,
                it can be difficult to set up something that sounds nice when
                you're done.  Here's a few tips on setting up an
                instrument:</para>

                <para><emphasis role="bold">Turn down the gain.</emphasis> Every
                time you have a gain knob (i.e. an amplifier), this is called
                a <emphasis>gain stage</emphasis>.  With every gain stage you
                have, it's easy to overdrive your signal &mdash; which means the
                signal gets distorted by clipping.  In addition, if you have two
                samples that, by themselves, peg your meters &mdash; what do you
                think happens when you combine them?  That's right, you
                overdrive the signal again.</para>

                <para>If things sound bad and distorted, start by turning down
                the gain setting on the layer... especially if it's larger than
                1.0.  Then turn down the instrument gain.  Then any gain on a
                LADSPA effect.  Then the fader on the mixer.  Then the master
                output fader.</para>

                <para><emphasis role="bold">Test samples at full
                velocity.</emphasis> Your sample will be played louder if the
                velocity is higher.  So, if you set everything to sound nice and
                full with velocity at 0.7, what will happen when you get a full
                velocity of 1.0?  (<emphasis>Hint: clipping.</emphasis>)</para>

                <para><emphasis role="bold">Try to use samples that are -6 dB
                max.</emphasis> Visually, this means samples that peak at only
                1/2 of full scale.  Otherwise, turn your layer gain to about
                .5.</para>

                <para><emphasis role="bold">Remove all DC offsets from the
                sample.</emphasis> In a sample editor, there is usually a line
                down the center of your sample's waveform.  This is the
                zero-line.  The beginning of your sample should be on this line.
                The end of your sample should also be on this line.  However, if
                your signal is a little above or a little below this line, you
                will hear a click at the beginning and the end of your sample
                whenever it is played.  If your sample editor doesn't provide
                any tools to fix a DC Offset problem, you can eliminate the
                noise by putting a slight fade-in/out at the ends of your
                sample.</para>

                <para><emphasis role="bold">The ADSR will not be longer than
                your sample.</emphasis> If you have a short sample, it doesn't
                matter how long you set the attack and delay &mdash; the sample
                will stop playing at the end.</para>

                <para><emphasis role="bold">Things change with the sample
                rate.</emphasis> If you have a really nice setup with all your
                parameters painstakenly
                tweaked... things <emphasis>will</emphasis> change if you change
                the sample rate of your audio card.  Many of Hydrogens internal
                settings and parameters are done based on how many samples go
                by, and not on how many seconds go by.  The sort of things that
                change are: anything time-base (like attack and release) and
                anything frequency based (like the cutoff frequency).</para>

        </section>
        </section>

        <section id="sect.ladspa">
                <title>LADSPA plugins</title>
                <para>Hydrogen can also add effects to sounds using any LADSPA plugin library. You need to have installed the LADSPA sources (available from <ulink url="http://www.ladspa.org"/>) and while this will give a rough idea of how it works you should really have a taste of the real thing installing one or more plugin libraries, it's as simple as a <command>scons &amp;&amp; scons install</command>.  Here are a few places to download plugin libraries:</para>

        <itemizedlist>
        <listitem><para>SWH-Plugins available at <ulink url="http://plugin.org.uk"/>. Note that before compiling these plugins you need the FFTW tarball from <ulink url="http://www.fftw.org"/>.</para></listitem>
        
        <listitem><para>CMT available at <ulink url="http://www.ladspa.org"/>.</para></listitem>
        
        <listitem><para>TAP available at <ulink url="http://tap-plugins.sf.net"/>.</para></listitem>
        
        </itemizedlist>

        <warning>
          <title>Plugins Kill</title>
          <para>A LADSPA plugin is compiled, executable code.  It is
          capable of hanging, crashing, freezing, screaching,
          overflowing buffers, and even phoning home.  If you start
          having issues with Hydrogen, disable your plugins and see if
          things improve.  Some plugins are not designed for real-time
          use, and some are just plain better than others.</para>
        </warning>
        
        <para>Once you have installed a few plugins open a song you'd like add an effect to and select an instrument that has a few beats in the pattern. In the Mixer click on 
        
        <inlinemediaobject>
                <imageobject>
                        <imagedata fileref="img/showFX_on.png" format="PNG" />
                </imageobject>
        </inlinemediaobject>
        
        and select one of the four available effect line Click on the Edit button (
        
        <inlinemediaobject>
                <imageobject>
                        <imagedata fileref="img/edit_off.png" format="PNG" />
                </imageobject>
        </inlinemediaobject>
        
        ), than on <quote>Select the FX</quote>: this will bring up another window (<xref linkend="fig.select_effect"/>) that lets you choose an effect amongst those installed, they are alphabetically sorted and categorized. Once you're done, adjust the level from the mixer and start playing. Each round knob in the FX part controls the level of its effect.
        
        <inlinemediaobject>
                <imageobject>
                        <imagedata fileref="img/MixerFXKnob.png" format="PNG"/>
                </imageobject>
        </inlinemediaobject>
        
        If you want to quickly enable/disable the effect click the Bypass (
        
        <inlinemediaobject>
                        <imageobject>
                                <imagedata fileref="img/bypass_over.png" format="PNG" />
                        </imageobject>
                </inlinemediaobject>) 
                
                
                button.</para>


                <figure id="fig.select_effect">
                <title>Select an Effect</title>
                <mediaobject>
                        <imageobject>
                                <imagedata fileref="img/MixerFXSelect.png" format="PNG" />
                        </imageobject>
                </mediaobject>
                </figure>
        
        </section>

</chapter>

<!--
##################
# CAPITOLO TERZO #
#################
-->

<chapter id="chap.create_song">
        <title>A new song</title>
        <section id="sect.song_vs_pattern">
                <title>"Song" mode and "Pattern" mode</title>
                <para>
                        This is just a quick-and-dirty walkthrough to Hydrogen. Refer to the tutorial for a more detailed overview.
                </para>
                
                <para>
                        Hydrogen has 2 main modes: "Pattern" mode and "Song" mode (refer to <xref linkend="sect.main_toolbar"/> for the buttons to activate). When "Pattern" mode is activated the current pattern is continously repeated, so to help changing it until we don't like it, while "Song" mode repeats only the current pattern: this is useful when putting together the patterns, to create the whole structure for the song.
                </para>
        </section>

        <section id="sect.create_pattern">
                <title>A new pattern</title>
                <para>
                We'll start from an empty song with an empty pattern, as created by default: "pattern" mode should be selected now. It is also possible to change name of the pattern. Now let's click on the <quote>Play</quote> button and while the pattern is playing let's add notes in the grid of the Song Editor (<xref linkend="fig.pattern_editor.2"/>) simply left_mouse_clicking on it: adjust grid resolution and BPM speed if needed. Rememeber some constraints of the grid: if you are working with a resolution of 16 you can't go back to 8 and remove a 16th note; same thing happens if you are working with a resolution of 8 and you try to insert a note in the middle of two bars (looking for a 16 bars precision): they will be placed on the previous or on the following 8th bar (unless you choose <quote>off</quote> from the Grid Resolution LCD, in this case you're free to place notes wherever you prefer). <emphasis role="bold">Be sure to select the correct pattern in the Song Editor before adding notes in the Pattern Editor!</emphasis>
                </para>

                <figure id="fig.pattern_editor.2">
                <title>The Pattern Editor</title>
                <mediaobject>
                        <imageobject>
                                <imagedata fileref="img/PatternEditor.png" format="PNG" />
                        </imageobject>
                </mediaobject>
                </figure>
        </section>

        <section id="sect.create_sequence">
                <title>A new sequence</title>
                <para>
                Once patterns are created (<xref linkend="fig.insert_notes"/>), we can copy/paste/delete them simply dragging with the mouse (activate the select mode for the Song Editor and keep pressed left mouse button to select those you want to move or copy).
                </para>

                <figure id="fig.insert_notes">
                <title>Inserting Notes in a Pattern</title>
                <mediaobject>
                        <imageobject>
                                <imagedata fileref="img/SongEditor.png" format="PNG" />
                        </imageobject>
                                </mediaobject>
                </figure>

        </section>
        
        <section id="sect.create_song.adjust_mixer">
                <title>Adjust from the mixer</title>
                <para>
                Of course we can always use the mixer window, either when creating or playing patterns.
                </para>
                
                <para>
                The Mixer frame (<xref linkend="fig.mixer.2"/>) is made of 32 independent tracks, each of these is binded to an
instrument, plus a "Master Output" line to adjust general output volume and a "FX" button to set effects. Every line features 3 buttons (
        
                <inlinemediaobject>
                        <imageobject>
                        <imagedata fileref="img/btn_play_on_mixer.png" format="PNG" />
                        </imageobject>
                </inlinemediaobject>
                
                <inlinemediaobject>
                        <imageobject>
                        <imagedata fileref="img/btn_solo_on.png" format="PNG" />
                        </imageobject>
                </inlinemediaobject>
                
                <inlinemediaobject>
                        <imageobject>
                        <imagedata fileref="img/btn_mute_on.png" format="PNG" />
                        </imageobject>
                </inlinemediaobject>
                
                ), pan adjust (
                
                <inlinemediaobject>
                        <imageobject>
                        <imagedata fileref="img/MixerPan.png" format="PNG" />
                        </imageobject>
                </inlinemediaobject>
                
                ), current maximum peak, volume fader and name of the track. Clicking on 
                
                <inlinemediaobject>
                        <imageobject>
                        <imagedata fileref="img/btn_solo_on.png" format="PNG" />
                        </imageobject>
                </inlinemediaobject>
                
                will play the selected instrument, cutting the others. The "Mute" 
button
                
                <inlinemediaobject>
                        <imageobject>
                        <imagedata fileref="img/btn_mute_on.png" format="PNG" />
                        </imageobject>
                </inlinemediaobject>

                , simply mute <emphasis>that</emphasis> instrument. The maximun peak indicates the maximun volume reached
from the instrument; the peak must be in a range of 0.0 and 1.0 (in <xref linkend="fig.mixer.2"/> you can see a few volumes too loud), otherwise it will get distorted producing a weird sound (especially with OSS audio driver), in this case it's better to set volume down; keep an eye on each vu-meter.
                </para>
                
                <figure id="fig.mixer.2">
                <title>The Mixer</title>
                <mediaobject>
                        <imageobject>
                                <imagedata fileref="img/Mixer.png" format="PNG" />
                        </imageobject>
                </mediaobject>
                </figure>
        </section>
</chapter>
<glossary id="glossary">
  <title>Glossary</title>

  <para>This is a glossary of general terms encountered when using Hydrogen,
  synthesizers, drums, or samplers.  The definitions in the text are simplified,
  but the definitions here are more general and have more explanation.  For
  example, the text of the manual would have you believe that an ADSR is the
  only kind of envelope generator, and could only ever control the volume.
  While it's simple for new users, it's not quite right.</para>

  <!--  ...  -->

  <!--   A   -->

  <glossentry id="def.adsr">
    <glossterm>ADSR</glossterm>
    <glossdef>
      <para>A type of envelope generator that allows you to control the
      <link linkend="def.attack">Attack</link>,
      <link linkend="def.decay">Decay</link>,
      <link linkend="def.sustain">Sustain</link>, and
      <link linkend="def.release">Release</link> parameters.
      Generally, the
      parameters are proportional to
      the <link linkend="def.velocity">velocity</link>.</para>

      <para>In Hydrogen, the ADSR envelope generator only controls the volume
      (attenuation).</para>

      <para>Read more about this in the Wikipedia
      Article <ulink url="http://en.wikipedia.org/wiki/ADSR_envelope">ADSR
      Envelope</ulink></para>

      <glossseealso otherterm="def.envelopegenerator"/>
      <glossseealso otherterm="def.attack"/>
      <glossseealso otherterm="def.decay"/>
      <glossseealso otherterm="def.sustain"/>
      <glossseealso otherterm="def.release"/>
    </glossdef>
  </glossentry>

  <glossentry id="def.attack">
    <glossterm>Attack</glossterm>
    <glossdef>
      <para>This is the first phase of an ADSR envelope, and is the amount
      of <emphasis>time</emphasis> to turn the parameter up from
      0 to full velocity after triggering the note.</para>

      <glossseealso otherterm="def.adsr"/>
    </glossdef>
  </glossentry>

  <glossentry id="def.attenuation">
    <glossterm>Attenuation</glossterm>
    <glossdef>
      <para>In filters and mixers, this the amount that a signal is reduced
      (volume).</para>

      <glossseealso otherterm="def.rolloff"/>
    </glossdef>
  </glossentry>

  <!--   B   -->

  <glossentry id="def.bandpassfilter">
    <glossterm>Band-Pass Filter</glossterm>
    <glossdef>
      <para>A filter that preserves a cetertain band of frequencies, and
      attenuates (silences) all others.  This is often done by combining a
      high-pass and a low-pass filter.</para>

      <glossseealso otherterm="def.filter"/>
      <glossseealso otherterm="def.highpassfilter"/>
      <glossseealso otherterm="def.lowpassfilter"/>
    </glossdef>
  </glossentry>

  <!--   C   -->

  <glossentry id="def.clipping">
    <glossterm>Clipping</glossterm>
    <glossdef>
      <para>A phenomenon that happens to a signal when the signal is
      too large for whatever is receiving it.  The peaks of the signal
      (which are normally smooth curves) get cut off straight at the
      max volume (clipped).  This distorts the sound and is usually
      undesirable.</para>

      <para>An example of clipping is when you play music louder than
      your speaker can handle.  Parts of the music sound harsh and
      fuzzy.</para>
    </glossdef>
  </glossentry>

  <glossentry id="def.cutoff">
    <glossterm>Cutoff Frequency</glossterm>
    <glossdef>
      <para>On high-pass and low-pass filters, this is the frequency that
      divides between those that pass, and those that are attenuated (silenced).
      In a high-pass resonance filter, or a low-pass resonance filter, the
      cutoff is also the frequency zone that gets boosted.</para>

      <para>For example, if you have a low-pass filter and you set the cutoff
      frequency high (i.e. 20kHz)... the filter will not affect the sound.  All
      the audible frequencies will pass through undisturbed.  As you lower the
      cutoff frequency to something like 40 Hz (the low string on a bass
      guitar), it sounds like someone is putting a blanket over the speaker.
      The higher frequencies are being attenuated above 30 Hz.</para>

      <glossseealso otherterm="def.filter"/>
      <glossseealso otherterm="def.highpassfilter"/>
      <glossseealso otherterm="def.lowpassfilter"/>
      <glossseealso otherterm="def.resonancefilter"/>
    </glossdef>
  </glossentry>

  <!--   D   -->

  <glossentry id="def.decay">
    <glossterm>Decay</glossterm>
    <glossdef>
      <para>After reaching full velocity from the attack, this is the amount
      of <emphasis>time</emphasis> to turn the parameter down
      from full velocity to the sustain level.</para>

      <glossseealso otherterm="def.adsr"/>
    </glossdef>
  </glossentry>

  <!--   E   -->

  <glossentry id="def.envelopegenerator">
    <glossterm>Envelope Generator</glossterm>
    <glossdef>
      <para>A way to control (change) a parameter over time as a response to
      triggering, holding, and releasing a note.</para>

      <!-- TRANSLATORS: This is a witty English expression that means, "Did I
           just say something really complicated, and you quit paying attention?
           I'll try it again a little more informally." -->
      <para>Did your eyes just glaze over? Let's try again:</para>

      <para>Imagine that you're playing a note on the keyboard and you have your
      other hand on a knob (volume, filter cutoff, etc.).  As you play the note,
      you twist the knob (often up, then down... or down, then up).  You do the
      same thing on each note.  That's what an envelope generator does.  See
      also <link linkend="def.adsr">ADSR</link></para>
    </glossdef>
  </glossentry>

  <!--   F   -->

  <glossentry id="def.fader">
    <glossterm>Fader</glossterm>
    <glossdef>
      <para>A slider control used to adjust the attenuation (volume) in a mixer.
      Faders always have an "audio" taper, which means that the attenuation
      amount changes on an exponential scale.</para>
    </glossdef>
  </glossentry>

  <glossentry id="def.filter">
    <glossterm>Filter</glossterm>
    <glossdef>
      <para>A device that changes a sound by attenuating specific frequencies.
      A tone knob is an example of a simple, low-pass filter.</para>

      <glossseealso otherterm="def.bandpassfilter"/>
      <glossseealso otherterm="def.highpassfilter"/>
      <glossseealso otherterm="def.lowpassfilter"/>
      <glossseealso otherterm="def.resonancefilter"/>
    </glossdef>
  </glossentry>

  <!--   G   -->

  <glossentry id="def.gain">
    <glossterm>Gain</glossterm>
    <glossdef>
      <para>In an amplifier, this adjust how much (or how little) a signal is
      amplified (volume).  A higher gain value is a louder signal.</para>
    </glossdef>
  </glossentry>

  <!--   H   -->

  <glossentry id="def.highpassfilter">
    <glossterm>High-Pass Filter</glossterm>
    <glossdef>
      <para>A filter that attenuates (silences) low frequencies, but allows high
      frequencies to pass through.</para>

      <glossseealso otherterm="def.filter"/>
      <glossseealso otherterm="def.cutoff"/>
    </glossdef>
  </glossentry>

  <!--   I   -->

  <glossentry id="def.instrument">
    <glossterm>Instrument</glossterm>
    <glossdef>
      <para>In Hydrogen, an instrument is a single noise-maker (like a bass drum
      kick, or a tom).</para>
    </glossdef>
  </glossentry>
  <!--   J   -->

  <!--   K   -->

  <!--   L   -->

  <glossentry id="def.layer">
    <glossterm>Layer</glossterm>
    <glossdef>
      <para>In an instrument you can load several different samples
      (each one called a <emphasis role="bold">layer</emphasis>), and
      have a different sample play depending on the velocity of the
      note.  Only one sample at a time will play.</para>

      <para>Suppose you have a sample of a floor tom being struck
      softly.  If you simply play the sample louder &mdash; it
      will <emphasis>not</emphasis> sound the same as a
      real tom that has been struck very hard.  If you wish to mimic
      this in your instrument, you can load one sample for soft
      playing, and a different sample for loud playing.</para>

      <glossseealso otherterm="def.instrument"/>
    </glossdef>
  </glossentry>

  <glossentry id="def.lowpassfilter">
    <glossterm>Low-Pass Filter</glossterm>
    <glossdef>
      <para>A filter that attenuates (silences) high frequences, but allows low
      frequencies to pass through.</para>

      <glossseealso otherterm="def.filter"/>
      <glossseealso otherterm="def.cutoff"/>
    </glossdef>
  </glossentry>

  <!--   M   -->

  <glossentry id="def.mute">
    <glossterm>Mute</glossterm>
    <glossdef>
      <para>To make no noise.  A setting on an instrument that prevents any
      audio output.</para>
    </glossdef>
  </glossentry>

  <glossentry id="def.mutegroup">
    <glossterm>Mute Group</glossterm>
    <glossdef>
      <para>A group of instruments (samples) that should mute (stop playing)
      immediately after another instrument in the group is triggered.</para>

      <para>This is typically used in hi-hats, where there's a different
      instrument (sample) for when the hi-hat is open or closed.  With a real
      hi-hat, the sound of the open hi-hat will stop as soon as you close it.
      However, if you use two samples &mdash; the open sound will continue even
      after you have triggered the closed sound.  By placing both instruments in
      the same mute group (group #1, for example)... triggering closed sound
      will immediately stop the open sound (and vice versa).</para>
    </glossdef>
  </glossentry>

  <!--   N   -->

  <!--   O   -->

  <glossentry id="def.octave">
    <glossterm>Octave</glossterm>
    <glossdef>
      <para>A span of frequencies where the top-most frequency is exactly twice
      the frequency of the bottom frequency.</para>

      <para>For example, the range 20 Hz to 40 Hz is an octave.  So is 120 Hz to
      240 Hz, and 575 Hz to 1150 Hz.  While the frequency differences are very
      different (20 Hz, 120 Hz, and 575 Hz, respectively), to the human ear
      they <emphasis>sound</emphasis> like the same
      distance.</para>
    </glossdef>
  </glossentry>

  <!--   P   -->

  <!--   Q   -->

  <!--   R   -->

  <glossentry id="def.release">
    <glossterm>Release</glossterm>
    <glossdef>
      <para>After the note is released, this is the amount
      of <emphasis>time</emphasis> to reduce the parameter from
      the sustain level to 0.</para>

      <glossseealso otherterm="def.adsr"/>
    </glossdef>
  </glossentry>

  <glossentry id="def.resonance">
    <glossterm>Resonance</glossterm>
    <glossdef>
      <para>When referring to a resonance filter, this is the parameter that
      determines how much of a boost (gain) to give the frequencies at the
      cutoff.</para>

      <glossseealso otherterm="def.resonancefilter"/>
    </glossdef>
  </glossentry>

  <glossentry id="def.resonancefilter">
    <glossterm>Resonance Filter</glossterm>
    <glossdef>
      <para>A filter that gives a large boost to a very narrow range of
      frequencies.  Typically it will be part of a high-pass or a low-pass
      filter, where the boosted frequencies are centered on the cut-off
      frequency.</para>

      <glossseealso otherterm="def.filter"/>
      <glossseealso otherterm="def.cutoff"/>
      <glossseealso otherterm="def.resonance"/>
    </glossdef>
  </glossentry>

  <glossentry id="def.rolloff">
    <glossterm>Roll-off</glossterm>
    <glossdef>
      <para>This is the amount that frequencies are attenuated (suppressed) as
      the frequency changes (typically measured in dB/octave).</para>

      <para>For example, in a low-pass filter the frequences below the cutoff
      frequency are not attenuated (they pass-through with the same volume).
      Same with the cutoff frequency.  As you go above the cutoff frequency, the
      frequencies that are near the cutoff frequency are not attenuated very
      much at all.  However, the frequencies that are much higher than the
      cutoff are attenuated (suppressed) a lot.  This is usually approximated by
      a straight line (on a log scale) and measured in in dB of attenuation per
      octave of frequency.</para>

      <glossseealso otherterm="def.attenuation"/>
      <glossseealso otherterm="def.filter"/>
    </glossdef>
  </glossentry>

  <!--   S   -->

  <glossentry id="def.sample">
    <glossterm>Sample</glossterm>
    <glossdef>
      <para>A short recording of a sound, typically between .1 and 3.0 seconds
      long.</para>
    </glossdef>
  </glossentry>

  <glossentry id="def.sustain">
    <glossterm>Sustain</glossterm>
    <glossdef>
      <para>The <emphasis>level</emphasis> to hold the parameter
      after finishing the decay time.  This level will be maintained until the
      not is released.</para>
      <glossseealso otherterm="def.adsr"/>
    </glossdef>
  </glossentry>

  <!--   T   -->

  <!--   U   -->

  <!--   V   -->

  <glossentry id="def.velocity">
    <glossterm>Velocity</glossterm>
    <glossdef>
      <para>How hard you hit a note.</para>

      <para>MIDI devices are required to send this information along with the
      note.  Synthesizers use this information to adjust several parameters on
      the sample (typically the volume).  In Hydrogen, it is only used to adjust
      how loud the sample is played back.</para>
    </glossdef>
  </glossentry>

  <!--   W   -->

  <!--   X   -->

  <!--   Y   -->

  <!--   Z   -->

</glossary>
</book>