♬ MidiWriterJS

MidiWriterJS is a JavaScript library providing an API for generating expressive multi-track MIDI files.

Note that the master branch is in active development so if you're looking for a tried and true stable version please use the latest release.

Source Documentation

Install

npm install midi-writer-js

Getting Started

var MidiWriter = require('midi-writer-js');

// Start with a new track
var track = new MidiWriter.Track();

// Define an instrument (optional):
track.addEvent(new MidiWriter.ProgramChangeEvent({instrument: 1}));

// Add some notes:
var note = new MidiWriter.NoteEvent({pitch: ['C4', 'D4', 'E4'], duration: '4'});
track.addEvent(note);

// Generate a data URI
var write = new MidiWriter.Writer(track);
console.log(write.dataUri());

Documentation

MidiWriter.Track()

• addEvent({event}, mapFunction)
• setTempo(tempo)
• addText(text)
• addCopyright(text)
• addTrackName(text)
• addInstrumentName(text)
• addMarker(text)
• addCuePoint(text)
• addLyric(text)
• setTimeSignature(numerator, denominator)

MidiWriter.NoteEvent({options})

The NoteEvent supports these options:

MidiWriter.Writer(tracks)

The Writer class provides a few ways to output the file:

• buildFile() Uint8Array
• base64() string
• dataUri() string
• stdout() file stream (cli)

Hot Cross Buns

Here's an example of how everyone's favorite song "Hot Cross Buns" could be written. Note use of the mapping function passed as the second argument of addEvent(). This can be used to apply specific properties to all events. With some street smarts you could also use it for programmatic crescendos and other property 'animation'.

var MidiWriter = require('midi-writer-js');

var track = new MidiWriter.Track();

track.addEvent([
		new MidiWriter.NoteEvent({pitch: ['E4','D4'], duration: '4'}),
		new MidiWriter.NoteEvent({pitch: ['C4'], duration: '2'}),
		new MidiWriter.NoteEvent({pitch: ['E4','D4'], duration: '4'}),
		new MidiWriter.NoteEvent({pitch: ['C4'], duration: '2'}),
		new MidiWriter.NoteEvent({pitch: ['C4', 'C4', 'C4', 'C4', 'D4', 'D4', 'D4', 'D4'], duration: '8'}),
		new MidiWriter.NoteEvent({pitch: ['E4','D4'], duration: '4'}),
		new MidiWriter.NoteEvent({pitch: ['C4'], duration: '2'})
	], function(event, index) {
    return {sequential: true};
  }
);

var write = new MidiWriter.Writer(track);
console.log(write.dataUri());

VexFlow Integration

MidiWriterJS can export MIDI from VexFlow voices, though this feature is still experimental. Current usage is to use MidiWriter.VexFlow.trackFromVoice(voice) to create a MidiWriterJS Track object:

// ...VexFlow code defining notes
var voice = create_4_4_voice().addTickables(notes);

var vexWriter = new MidiWriter.VexFlow();
var track = vexWriter.trackFromVoice(voice);
var writer = new MidiWriter.Writer([track]);
console.log(writer.dataUri());