A pure-TypeScript MIDI file generator with zero dependencies. A modern rewrite of jsmidgen.

Install

npm install @scribbletune/midi

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.

import { writeFileSync } from "fs";
import { File, Track } from "@scribbletune/midi";
const file = new File();
const track = new 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);
writeFileSync("test.mid", file.toUint8Array());

This will create a MIDI file that plays an ascending C major scale starting at middle C.

Fluent API

The library supports a fluent (chained) style using method aliases:

import { writeFileSync } from "fs";
import { File } from "@scribbletune/midi";
const file = new 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)
  // switch channel 0 from grand piano (default, number 0)
  // to church organ (number 19)
  .instrument(0, 19)
  // create a chord by starting multiple notes without a time gap
  .noteOn(0, "c4", 64)
  .noteOn(0, "e4")
  .noteOn(0, "g4")
  // stop all notes at once
  .noteOff(0, "c4", 47)
  .noteOff(0, "e4")
  .noteOff(0, "g4")
  // alternatively, use addChord for convenience
  .addChord(0, ["c4", "e4", "g4"], 64)
  .setTempo(120)
  .setTimeSignature(4, 4);
writeFileSync("test.mid", file.toUint8Array());

Note the use of instrument() (alias of setInstrument()), and noteOn()/noteOff() (aliases of addNoteOn()/addNoteOff()) to produce chords.

Imports

// Named imports (recommended)
import { File, Track, MidiEvent, MetaEvent, Util } from "@scribbletune/midi";
// Default namespace import (backwards-compatible style)
import Midi from "@scribbletune/midi";
new Midi.File();
// CommonJS
const Midi = require("@scribbletune/midi");
const { File, Track } = require("@scribbletune/midi");

Reference

File

• new File([config]) - Create a new MIDI file. Optional config.ticks sets ticks per beat (default 128, must be integer 1-32767).
• addTrack() - Add a new Track and return it.
• addTrack(track) - Add an existing Track and return the File.
• toBytes() - Serialize to a string of bytes.
• toUint8Array() - Serialize to a Uint8Array.
• toBlob([genericType]) - Serialize to a Blob. Uses audio/x-midi MIME type by default, or application/octet-stream if genericType is true.

Track

Time and duration are specified in "ticks" (128 ticks per beat by default). A quarter note = 128 ticks.

Pitch can be a note name with octave (c4, a#3, eb5) or a MIDI number (60). Middle C is c4 or 60.

• addNote(channel, pitch, duration[, time[, velocity]]) - Add a complete note (on + off). time adds a rest before the note. velocity sets strike intensity (default 90).
• addNoteOn(channel, pitch[, time[, velocity]]) - Start a note.
• addNoteOff(channel, pitch[, time[, velocity]]) - End a note.
• addChord(channel, pitches, duration[, velocity]) - Add a chord from an array of pitches.
• setInstrument(channel, instrument[, time]) - Change instrument (0-based, see General MIDI, subtract 1).
• setTempo(bpm[, time]) - Set tempo in beats per minute.
• setTimeSignature(numerator, denominator[, time]) - Set time signature. Denominator must be a power of 2.
• setKeySignature(accidentals[, minor[, time]]) - Set key signature. Positive = sharps, negative = flats.

All Track methods return this for chaining. Each method also has a shorthand alias: note, noteOn, noteOff, chord, instrument, tempo, timeSignature, keySignature.

License

MIT