♬ 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.
Install
npm install midi-writer-jsGetting 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:
| Name | Type | Description |
|---|---|---|
| pitch | string or array | Each pitch can be a string or valid MIDI note code. Format for string is C#4. Pro tip: You can use the output from tonal functions to build scales, chords, intervals, etc. in this parameter. |
| duration | string or array |
How long the note should sound.
|
| wait | string or array | How long to wait before sounding note (rest). Takes same values as duration. |
| sequential | boolean | If true then array of pitches will be played sequentially as opposed to simulatanously. Default: false |
| velocity | number | How loud the note should sound, values 1-100. Default: 50 |
| repeat | number | How many times this event should be repeated. Default: 1 |
| channel | number | MIDI channel to use. Default: 1 |
| grace | string or array | Grace note to be applied to note event. Takes same value format as pitch |
| startTick | number | Specific tick where this event should be played. If this parameter is supplied then wait is disregarded if also supplied. |
MidiWriter.Writer(tracks)
The Writer class provides a few ways to output the file:
buildFile()Uint8Arraybase64()stringdataUri()stringstdout()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());
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