phpman > man > MIDI(3pm)

NAME
    MIDI - read, compose, modify, and write MIDI files

SYNOPSIS
     use MIDI;
     use strict;
     use warnings;
     my @events = (
       ['text_event',0, 'MORE COWBELL'],
       ['set_tempo', 0, 450_000], # 1qn = .45 seconds
     );

     for (1 .. 20) {
       push @events,
         ['note_on' , 90,  9, 56, 127],
         ['note_off',  6,  9, 56, 127],
       ;
     }
     foreach my $delay (reverse(1..96)) {
       push @events,
         ['note_on' ,      0,  9, 56, 127],
         ['note_off', $delay,  9, 56, 127],
       ;
     }

     my $cowbell_track = MIDI::Track->new({ 'events' => \@events });
     my $opus = MIDI::Opus->new(
      { 'format' => 0, 'ticks' => 96, 'tracks' => [ $cowbell_track ] } );
     $opus->write_to_file( 'cowbell.mid' );

DESCRIPTION
    This suite of modules provides routines for reading, composing, modifying, and writing MIDI
    files.

    From FOLDOC ("http://wombat.doc.ic.ac.uk/foldoc/"):

        MIDI, Musical Instrument Digital Interface

        <multimedia, file format> (MIDI /mi'-dee/, /mee'-dee/) A hardware specification and protocol
        used to communicate note and effect information between synthesisers, computers, music
        keyboards, controllers and other electronic music devices. [...]

        The basic unit of information is a "note on/off" event which includes a note number (pitch)
        and key velocity (loudness). There are many other message types for events such as pitch
        bend, patch changes and synthesizer-specific events for loading new patches etc.

        There is a file format for expressing MIDI data which is like a dump of data sent over a
        MIDI port. [...]

COMPONENTS
    The MIDI-Perl suite consists of these modules:

    MIDI (which you're looking at), MIDI::Opus, MIDI::Track, MIDI::Event, MIDI::Score, and
    MIDI::Simple. All of these contain documentation in pod format. You should read all of these
    pods.

    The order you want to read them in will depend on what you want to do with this suite of
    modules: if you are focused on manipulating the guts of existing MIDI files, read the pods in
    the order given above.

    But if you aim to compose music with this suite, read this pod, then MIDI::Score and
    MIDI::Simple, and then skim the rest.

INTRODUCTION
    This suite of modules is basically object-oriented, with the exception of MIDI::Simple. MIDI
    opuses ("songs") are represented as objects belonging to the class MIDI::Opus. An opus contains
    tracks, which are objects belonging to the class MIDI::Track. A track will generally contain a
    list of events, where each event is a list consisting of a command, a delta-time, and some
    number of parameters. In other words, opuses and tracks are objects, and the events in a track
    comprise a LoL (and if you don't know what an LoL is, you must read perllol).

    Furthermore, for some purposes it's useful to analyze the totality of a track's events as a
    "score" -- where a score consists of notes where each event is a list consisting of a command, a
    time offset from the start of the track, and some number of parameters. This is the level of
    abstraction that MIDI::Score and MIDI::Simple deal with.

    While this suite does provide some functionality accessible only if you're comfortable with
    various kinds of references, and while there are some options that deal with the guts of MIDI
    encoding, you can (I hope) get along just fine with just a basic grasp of the MIDI "standard",
    and a command of LoLs. I have tried, at various points in this documentation, to point out what
    things are not likely to be of use to the casual user.

GOODIES
    The bare module MIDI.pm doesn't *do* much more than "use" the necessary component submodules
    (i.e., all except MIDI::Simple). But it does provide some hashes you might find useful:

    %MIDI::note2number and %MIDI::number2note
        %MIDI::number2note corresponds MIDI note numbers to a more comprehensible representation
        (e.g., 68 to 'Gs4', for G-sharp, octave 4); %MIDI::note2number is the reverse. Have a look
        at the source to see the contents of the hash.

    %MIDI::patch2number and %MIDI::number2patch
        %MIDI::number2patch corresponds General MIDI patch numbers (0 to 127) to English names
        (e.g., 79 to 'Ocarina'); %MIDI::patch2number is the reverse. Have a look at the source to
        see the contents of the hash.

    %MIDI::notenum2percussion and %MIDI::percussion2notenum
        %MIDI::notenum2percussion corresponds General MIDI Percussion Keys to English names (e.g.,
        56 to 'Cowbell') -- but note that only numbers 35 to 81 (inclusive) are defined;
        %MIDI::percussion2notenum is the reverse. Have a look at the source to see the contents of
        the hash.

BRIEF GLOSSARY
    This glossary defines just a few terms, just enough so you can (hopefully) make some sense of
    the documentation for this suite of modules. If you're going to do anything serious with these
    modules, however, you *should really* invest in a good book about the MIDI standard -- see the
    References.

    channel: a logical channel to which control changes and patch changes apply, and in which MIDI
    (note-related) events occur.

    control: one of the various numeric parameters associated with a given channel. Like S registers
    in Hayes-set modems, MIDI controls consist of a few well-known registers, and beyond that, it's
    patch-specific and/or sequencer-specific.

    delta-time: the time (in ticks) that a sequencer should wait between playing the previous event
    and playing the current event.

    meta-event: any of a mixed bag of events whose common trait is merely that they are similarly
    encoded. Most meta-events apply to all channels, unlike events, which mostly apply to just one
    channel.

    note: my oversimplistic term for items in a score structure.

    opus: the term I prefer for a piece of music, as represented in MIDI. Most specs use the term
    "song", but I think that this falsely implies that MIDI files represent vocal pieces.

    patch: an electronic model of the sound of a given notional instrument.

    running status: a form of modest compression where an event lacking an event command byte (a
    "status" byte) is to be interpreted as having the same event command as the preceding event --
    which may, in turn, lack a status byte and may have to be interpreted as having the same event
    command as *its* previous event, and so on back.

    score: a structure of notes like an event structure, but where notes are represented as single
    items, and where timing of items is absolute from the beginning of the track, instead of being
    represented in delta-times.

    song: what some MIDI specs call a song, I call an opus.

    sequencer: a device or program that interprets and acts on MIDI data. This prototypically refers
    to synthesizers or drum machines, but can also refer to more limited devices, such as mixers or
    even lighting control systems.

    status: a synonym for "event".

    sysex: a chunk of binary data encapsulated in the MIDI data stream, for whatever purpose.

    text event: any of the several meta-events (one of which is actually called 'text_event') that
    conveys text. Most often used to just label tracks, note the instruments used for a track, or to
    provide metainformation about copyright, performer, and piece title and author.

    tick: the timing unit in a MIDI opus.

    variable-length encoding: an encoding method identical to what Perl calls the 'w' (BER, Basic
    Encoding Rules) pack/unpack format for integers.

SEE ALSO
    <http://interglacial.com/~sburke/midi-perl/> -- the MIDI-Perl homepage on the Interwebs!

    <http://search.cpan.org/search?m=module&q=MIDI&n=100> -- All the MIDI things in CPAN!

REFERENCES
    Christian Braut. *The Musician's Guide to Midi.* ISBN 0782112854. [This one is indispensible,
    but sadly out of print. Look at abebooks.com for it maybe --SMB]

    Langston, Peter S. 1998. "Little Music Languages", p.587-656 in: Salus, Peter H,. editor in
    chief, /Handbook of Programming Languages/, vol. 3. MacMillan Technical, 1998. [The volume it's
    in is probably not worth the money, but see if you can at least glance at this article anyway.
    It's not often you see 70 pages written on music languages. --SMB]

COPYRIGHT
    Copyright (c) 1998-2005 Sean M. Burke. All rights reserved.

    This library is free software; you can redistribute it and/or modify it under the same terms as
    Perl itself.

AUTHORS
    Sean M. Burke "sburke AT cpan.org" (until 2010)

    Darrell Conklin "conklin AT cpan.org" (from 2010)