go-midi

go-midi provides reading and writing standard MIDI file.

Installation

go get -u github.com/moutend/go-midi

Examples

Print All Text Events

The following program reads a file named music.mid and then prints all text data.

package main

import (
	"fmt"
	"io/ioutil"

	midi "github.com/moutend/go-midi"
)

func main() {
	file, err := ioutil.ReadFile("music.mid")
	if err != nil {
		panic(err)
	}

	midiData, err := midi.Parse(file)
	if err != nil {
		panic(err)
	}

	for _, track := range midiData.Tracks {
		for _, event := range track.Events {
			switch event.(type) {
			case *midi.TextEvent:
				fmt.Printf("%s\n", event.(*midi.TextEvent).Text())
			}
		}
	}
}

Normalize Velocity of Note-on Event

The following program reads a file named input.mid, set the velocity of all note-on events to 127 and creates a new file named output.mid.

package main

import (
	"io/ioutil"

	midi "github.com/moutend/go-midi"
)

func main() {
	file, err := ioutil.ReadFile("input.mid")
	if err != nil {
		panic(err)
	}

	midiData, err := midi.Parse(file)
	if err != nil {
		panic(err)
	}

	for _, track := range midiData.Tracks {
		for _, event := range track.Events {
			switch event.(type) {
			case *midi.NoteOnEvent:
				event.(*midi.NoteOnEvent).SetVelocity(127)
			}
		}
	}
	err = ioutil.WriteFile("output.mid", midiData.Serialize(), 0644)
	if err != nil {
		panic(err)
	}
}

Create C Major Chord

The following program creates a MIDI file which plays C major chord.

package main

import (
	"io/ioutil"

	midi "github.com/moutend/go-midi"
)

func main() {
	deltaTime1, _ := midi.NewDeltaTime(0)
	deltaTime2, _ := midi.NewDeltaTime(960)

	noteOnC4, _ := midi.NewNoteOnEvent(deltaTime1, 0, midi.C4, 127)
	noteOnE4, _ := midi.NewNoteOnEvent(deltaTime1, 0, midi.E4, 127)
	noteOnG4, _ := midi.NewNoteOnEvent(deltaTime1, 0, midi.G4, 127)

	noteOffC4, _ := midi.NewNoteOffEvent(deltaTime2, 0, midi.C4, 0)
	noteOffE4, _ := midi.NewNoteOffEvent(deltaTime1, 0, midi.E4, 0)
	noteOffG4, _ := midi.NewNoteOffEvent(deltaTime1, 0, midi.G4, 0)

	endOfTrack, _ := midi.NewEndOfTrackEvent(deltaTime2)

	track := &midi.Track{
		Events: make([]midi.Event, 0),
	}

	track.Events = append(track.Events, noteOnC4)
	track.Events = append(track.Events, noteOnE4)
	track.Events = append(track.Events, noteOnG4)

	track.Events = append(track.Events, noteOffC4)
	track.Events = append(track.Events, noteOffE4)
	track.Events = append(track.Events, noteOffG4)

	track.Events = append(track.Events, endOfTrack)

	m := midi.MIDI{}
	m.TimeDivision().SetBPM(240)
	m.Tracks = make([]*midi.Track, 1)
	m.Tracks[0] = track

	ioutil.WriteFile("oo.mid", m.Serialize(), 0644)
}

Numbering of nNotes

There are two conventions for notes in MIDI. The most common is where C3 is 0x3c and the another is where C4 is 0x3c. In this package, where C3 is 0x3c.

MIDI Files for Testing

The MIDI files located at testdata were composed by Nao. Check her great works:

• 星のカービィ　MIDI - みかんの旅

About MIDI

• MIDI File Format Specifications · colxi/midi-parser-js Wiki
• 0xff21 and 0xff20 in MIDI
• OpenMIDIProject - Documentations

Contributing

1. Fork (https://github.com/moutend/go-midi/fork)
2. Create a feature branch
3. Add changes
4. Run go fmt
5. Commit your changes
6. Open a new Pull Request

LICENSE

MIT

Author

Yoshiyuki Koyanagi