https://github.com/dingram/jsmidgen

A pure-JavaScript MIDI generator
https://github.com/dingram/jsmidgen

Last synced: 3 months ago
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A pure-JavaScript MIDI generator

• Host: GitHub
• URL: https://github.com/dingram/jsmidgen
• Owner: dingram
• Created: 2012-04-25T19:12:22.000Z (over 12 years ago)
• Default Branch: master
• Last Pushed: 2017-10-24T15:57:59.000Z (about 7 years ago)
• Last Synced: 2024-04-27T03:01:40.516Z (7 months ago)
• Language: JavaScript
• Size: 46.9 KB
• Stars: 220
• Watchers: 6
• Forks: 34
• Open Issues: 22
• Metadata Files:
  • Readme: README.md

Awesome Lists containing this project

• awesome-javascript-audio - dingram/jsmidgen - generate MIDI files from javascript (Libraries: Web MIDI API / Web MIDI API)

README

        
# jsmidgen, a pure-JavaScript MIDI file library

## Introduction

jsmidgen (pronounced jay-smidgen or jer-smidgen) is a library that can be used

to generate MIDI files in JavaScript. It currently provides output as a string,

but there are plans to provide multiple output formats, including base64 and

data URI.

## Example Usage

The MIDI file structure is made up of one or more tracks, which contain one or

more events. These events can be note on/off events, instrument changes, tempo

changes, or more exotic things. A basic example is shown below:

    var fs = require('fs');

    var Midi = require('jsmidgen');

    var file = new Midi.File();

    var track = new Midi.Track();

    file.addTrack(track);

    track.addNote(0, 'c4', 64);

    track.addNote(0, 'd4', 64);

    track.addNote(0, 'e4', 64);

    track.addNote(0, 'f4', 64);

    track.addNote(0, 'g4', 64);

    track.addNote(0, 'a4', 64);

    track.addNote(0, 'b4', 64);

    track.addNote(0, 'c5', 64);

    fs.writeFileSync('test.mid', file.toBytes(), 'binary');

This example will create a MIDI file that will play an ascending C major scale,

starting at middle C.

## Fluid API

This library also has rudimentary support for a fluid (chained) style:

    file = new Midi.File();

    file

      .addTrack()

        .note(0, 'c4', 32)

        .note(0, 'd4', 32)

        .note(0, 'e4', 32)

        .note(0, 'f4', 32)

        .note(0, 'g4', 32)

        .note(0, 'a4', 32)

        .note(0, 'b4', 32)

        .note(0, 'c5', 32)

        // church organ

        .instrument(0, 0x13)

        // by skipping the third arguments, we create a chord (C major)

        .noteOn(0, 'c4', 64)

        .noteOn(0, 'e4')

        .noteOn(0, 'g4')

        // by skipping the third arguments again, we stop all notes at once

        .noteOff(0, 'c4', 47)

        .noteOff(0, 'e4')

        .noteOff(0, 'g4')

        //alternatively, a chord may be created with the addChord function

        .addChord(0, ['c4', 'e4', 'g4'], 64)

        .noteOn(0, 'c4', 1)

        .noteOn(0, 'e4')

        .noteOn(0, 'g4')

        .noteOff(0, 'c4', 384)

        .noteOff(0, 'e4')

        .noteOff(0, 'g4')

        ;

    fs.writeFileSync('test2.mid', file.toBytes(), 'binary');

Note the use of `setInstrument()` to change to a church organ midway through,

and the use of `addNoteOn()`/`addNoteOff()` to produce chords.

## Reference

### Midi.File

 - `addTrack()` - Add a new Track object to the file and return the new track

 - `addTrack(track)` - Add the given Track object to the file and return the file

### Midi.Track

Time and duration are specified in "ticks", and there is a hardcoded

value of 128 ticks per beat. This means that a quarter note has a duration of 128.

Pitch can be specified by note name with octave (`a#4`) or by note number (`60`).

Middle C is represented as `c4` or `60`.

 - `addNote(channel, pitch, duration[, time[, velocity]])`

   **Add a new note with the given channel, pitch, and duration**

   - If `time` is given, delay that many ticks before starting the note

   - If `velocity` is given, strike the note with that velocity

 - `addNoteOn(channel, pitch[, time[, velocity]])`

   **Start a new note with the given channel and pitch**

   - If `time` is given, delay that many ticks before starting the note

   - If `velocity` is given, strike the note with that velocity

 - `addNoteOff(channel, pitch[, time[, velocity]])`

   **End a note with the given channel and pitch**

   - If `time` is given, delay that many ticks before ending the note

   - If `velocity` is given, strike the note with that velocity

 - `addChord(channel, chord[, velocity])`

   **Add a chord with the given channel and pitches**

   - Accepts an array of pitches to play as a chord

   - If `velocity` is given, strike the chord with that velocity

 - `setInstrument(channel, instrument[, time])`

   **Change the given channel to the given instrument**

   - If `time` is given, delay that many ticks before making the change

 - `setTempo(bpm[, time])`

   **Set the tempo to `bpm` beats per minute**

   - If `time` is given, delay that many ticks before making the change