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MIDI - read, compose, modify, and write MIDI files
MIDI - read, compose, modify, and write MIDI files
use MIDI;
$chimes_track = MIDI::Track->new({ 'events' => [
['text_event',0, 'www.ely.anglican.org/parishes/camgsm/chimes.html'],
['text_event',0, 'Lord through this hour/ be Thou our guide'],
['text_event',0, 'so, by Thy power/ no foot shall slide'],
['text_event',0, '(coded at ' . scalar(localtime) . ' )'],
['patch_change', 0, 1, 8], # Patch 8 = Celesta
map( (['note_on',0,1,$_->[0],96], ['note_off',$_->[1],1,$_->[0],0]),
[25,96],[29,96],[27,96],[20,192],[25,96],[27,96],[29,96],[25,192],
[29,96],[25,96],[27,96],[20,192],[20,96],[27,96],[29,96],[25,192],
)# [Note,Duration] ==> ['note_on',0,1, N ,96], ['note_off', D ,1, N ,0]
] });
$chimes = MIDI::Opus->new(
{ 'format' => 0, 'ticks' => 96, 'tracks' => [ $chimes_track ] } );
$chimes->write_to_file('chimes.mid');
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
E<lt>multimedia, file formatE<gt> (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. [...]
The MIDI-Perl suite consists of these modules:
MIDI (which you're looking at), the MIDI::Opus manpage, the MIDI::Track manpage,
the MIDI::Event manpage, the MIDI::Score manpage, and
the MIDI::Simple manpage. 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
the MIDI::Score manpage and the MIDI::Simple manpage, and then skim the rest.
(For your reference, there is also a document in pod format which is
not itself an actual module: the MIDI::Filespec manpage. It is an old version
of the MIDI file specification.)
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.
Maybe have a MIDI cookbook of commonly used short scripts?
A PLEA: Currently this suite can only read/write MIDI data from/to
MIDI files. However, it would be desirable to have realtime access
to a MIDI device -- at least on systems where a MIDI device (whether
thru a hardware port or as a virtual sequencer in a sound card) is
accessable as a virtual file (/dev/midi0, /dev/midi,
/dev/sequencer, or whatever). However, I have no such MIDI devices
(much less ports) at hand for development and testing. But if you
have such devices (I'm thinking a Linuxer with a synth hooked to their
MIDI port), and if you want to help me experiment with directly
accessing them from Perl, then please email me. I already have a
pretty good idea of how it should work -- but as always, the proof is
as much in the pudding as the devil is in the details.
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 correponds 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 correponds 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 correponds 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.
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.
Christian Braut. The Musician's Guide to Midi. ISBN 0782112854.
[This one is indispensible --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]
I'll keep a list of other references and good stuff at
the URL http://www.speech.cs.cmu.edu/~sburke/pub/perl_midi/
Copyright (c) 1998-2002 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.
Sean M. Burke sburke@cpan.org
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