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/"):

COMPONENTS¶

The MIDI-Perl suite consists of these modules:

MIDI (which you're looking at), MIDI::Opus, MIDI::Track,MIDI::Event, MIDI::Score, andMIDI::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 dowith this suite of modules: if you are focused on manipulating theguts 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, thenMIDI::Score and MIDI::Simple, and then skim the rest.

INTRODUCTION¶

This suite of modules is basically object-oriented, with the exceptionof MIDI::Simple. MIDI opuses ("songs") are represented as objectsbelonging to the class MIDI::Opus. An opus contains tracks, which areobjects belonging to the class MIDI::Track. A track will generallycontain a list of events, where each event is a list consisting of acommand, a delta-time, and some number of parameters. In other words,opuses and tracks are objects, and the events in a track comprise aLoL (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 ofa track's events as a "score" -- where a score consists of notes whereeach event is a list consisting of a command, a time offset from thestart of the track, and some number of parameters. This is the levelof abstraction that MIDI::Score and MIDI::Simple deal with.

While this suite does provide some functionality accessible only ifyou're comfortable with various kinds of references, and while thereare some options that deal with the guts of MIDI encoding, you can (Ihope) get along just fine with just a basic grasp of the MIDI"standard", and a command of LoLs. I have tried, at various points inthis documentation, to point out what things are not likely to be ofuse 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 ofmodules. 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 homepageon the Interwebs!

<http://search.cpan.org/search?m=module&q=MIDI&n=100> -- All the MIDIthings 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 probablynot worth the money, but see if you can at least glance at thisarticle anyway. It's not often you see 70 pages written on musiclanguages. --SMB]

COPYRIGHT¶

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

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

AUTHORS¶

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

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