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npm install @tonejs/midi


Midi makes it straightforward to read and write MIDI files with Javascript. It uses midi-file for parsing and writing.



const { Midi } = require('@tonejs/midi')

Typescript / ES6

import { Midi } from '@tonejs/midi'


<script src=""></script>
const midi = new Midi()

Basic Example

// load a midi file in the browser
const midi = await Midi.fromUrl("path/to/midi.mid")
//the file name decoded from the first track
const name =
//get the tracks
midi.tracks.forEach(track => {
  //tracks have notes and controlChanges

  //notes are an array
  const notes = track.notes
  notes.forEach(note => {
    //note.midi, note.time, note.duration,

  //the control changes are an object
  //the keys are the CC number
  //they are also aliased to the CC number's common name (if it has one)
  track.controlChanges.sustain.forEach(cc => {
    // cc.ticks, cc.value, cc.time

  //the track also has a channel and instrument


The data parsed from the midi file looks like this:

  // the transport and timing data
  header: {
    name: String,                     // the name of the first empty track, 
                                      // which is usually the song name
    tempos: TempoEvent[],             // the tempo, e.g. 120
    timeSignatures: TimeSignatureEvent[],  // the time signature, e.g. [4, 4],

    PPQ: Number                       // the Pulses Per Quarter of the midi file
                                      // this is read only

  duration: Number,                   // the time until the last note finishes

  // an array of midi tracks
  tracks: [
      name: String,                   // the track name if one was given

      channel: Number,                // channel
                                      // the ID for this channel; 9 and 10 are
                                      // reserved for percussion
      notes: [
          midi: Number,               // midi number, e.g. 60
          time: Number,               // time in seconds
          ticks: Number,              // time in ticks
          name: String,               // note name, e.g. "C4",
          pitch: String,              // the pitch class, e.g. "C",
          octave : Number,            // the octave, e.g. 4
          velocity: Number,           // normalized 0-1 velocity
          duration: Number,           // duration in seconds between noteOn and noteOff

      // midi control changes
      controlChanges: {
        // if there are control changes in the midi file
        '91': [
            number: Number,           // the cc number
            ticks: Number,            // time in ticks
            time: Number,             // time in seconds
            value: Number,            // normalized 0-1

      instrument: {                   // and object representing the program change events
        number : Number,              // the instrument number 0-127
        family: String,               // the family of instruments, read only.
        name : String,                // the name of the instrument
        percussion: Boolean,          // if the instrument is a percussion instrument

Raw Midi Parsing

If you are using Node.js or have the raw binary string from the midi file, just use the parse method:

const midiData = fs.readFileSync("test.mid")
const midi = new Midi(midiData)

Encoding Midi

You can also create midi files from scratch or by modifying an existing file.

// create a new midi file
var midi = new Midi()
// add a track
const track = midi.addTrack()
  midi : 60,
  time : 0,
  duration: 0.2
  name : 'C5',
  time : 0.3,
  duration: 0.1
  number : 64,
  value : 127,
  time : 0.2
// write the output
fs.writeFileSync("output.mid", new Buffer(midi.toArray()))


Thank you midi-file!