Midian

A set of tools for parsing an extended dialect of MML and emitting MIDI. The parts can be easily repurposed.

Installation

Or install it yourself as:

gem install midian

Or, if you want to use it in your own library, add this line to your application's Gemfile:

gem 'midian'

And then execute:

bundle

Usage

Setup

Make sure you have the gem installed.

Make sure you have Homebrew installed.

brew install fluid-synth wget
wget -c http://thefifthcircuit.stuff.s3.amazonaws.com/arachno-soundfont-10-sf2.zip
unzip arachno-soundfont-10-sf2.zip
rm arachno-soundfont-*.zip
mv arachno-soundfont-* arachno-soundfont

Basics

Put some MML in a file, like this:

# Put some MML in a file.
echo 'T a4bc8 a4b>g8<' > test.mml

# Use Midian to generate a MIDI file.
cat test.mml | midian > test.mid

# Test out the MIDI file using fluidsynth.
fluidsynth 'arachno-soundfont/Arachno SoundFont - Version 1.0.sf2' test.mid

You can also pipe MML directly into Midian.

echo 'T a4bc8 a4b>g8<' | midian > test.mid

You can inspect the MIDI hex output safely like so:

cat test.mml | midian | midian-hexdump

You can run the whole pipeline manually like so:

echo 'T abcd4' |
  midian-preprocessor |
  midian-parser |
  midian-organizer |
  midian-shoehorn

This allows for stages of the pipeline to be developed in isolation.

Extended MML syntax

Whitespace is almost entirely insignificant. It can be omitted or added in nearly any circumstance.

Basic MML

o4 - Set the current octave to 4.
< - Lower current octave by 1.
> - Raise current octave by 1.
v80 - Set MIDI velocity to 80.
d4 - Set default duration to 4 (quarter note).
n36 - Play MIDI note 36 (a C) with the default velocity and duration.
t120 - Change the song tempo to 120.
a - Play an A in the current octave.
a4 - Play an A as a quarter note.
ab4 - Play an A, then a B, as quarter notes.
a4bc8 - Play an A as a quarter note followed by a B and a C as eighth notes.
r4 - Rest for a quarter note.
T - Switch to track T. Track names are all-uppercase alphanumeric words. Delta times are tracked independently for each track.

Valid notes are a, b, c, d, e, f, g.

Valid durations are 32, 24, 16, 12, 9, 8, 6, 4, 3, 2, 1. Note that this allows for triplets. Durations may be appended with any number of dots. Each dot will add half-again the duration to itself.

Lines beginning with ; are comments.

Lines beginning with # are directives. The only directive that is handled right now is #Track, which allows for mapping of tracks to a MIDI channel (see below).

Directives

#Track T 1

Map the track named T to MIDI channel 1.

More directives will come shortly. See midian/lib/midian/directive_context.rb.

Preprocessor directives (macros)

{{code}}

Code is evaluated as Ruby, and if it returns a value, the value will be printed into the resulting code. You can use this to create loops:

{{4.times do}}a4bc8{{end}}

More directives will come shortly. See midian/lib/midian/preprocessor.rb.

Inline Ruby code

[[code]]

Inline Ruby code. Code is evaluated at evaluation time, and this can be used to add new functionality to the interpreter. For example:

[[mark :foo]] - Store current MIDI delta time in a mark named :foo.

[[jump :foo]] - Rewind MIDI delta time to the point in time marked :foo.

[[sysex '10421240007F0041']] - Send sysex hex string as hex bytes. It will automatically be prepended with f0 and the length, and appended with f7.

More directives will come shortly. See midian/lib/midian/ruby_context.rb.

TODO

MML features:

Ties (&)
Chords using ( and )
! variables
@ variables
Loops using [ and ]
Setting of MIDI track names
More raw MIDI Ruby directives
Ignored | for readability
Loops using |: and :|

Other:

Start adding tests
Document the various stages

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/midian. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

rjungemann / midian