deno_midi

⚠️ This is a work in progress and may be subject to breaking changes until it hits 1.0. ⚠️

A Deno wrapper for the RtMidi C++ library that provides realtime MIDI I/O.

It uses pre-built binaries of the 6.0.0 version of the library for Windows, Linux and MacOS (x64 and arm64), so no need to install any dependencies. They’re built from my fork of the RtMidi library that adds some extra features.

It uses Deno FFI to call the C++ library. The bindings have been generated thanks to the great help from Aapo Alasuutari and his libclang_deno bindings generator. He’s also the author of the denonomicon which is a great resource for FFI.

Usage

Since it uses FFI, it should be run with the --unstable flag.

Basic check

import { midi } from "https://deno.land/x/deno_midi/mod.ts";

console.log(midi.getVersion()); // Should print 6.0.0

Midi Input

import { midi } from "https://deno.land/x/deno_midi/mod.ts";

const midi_in = new midi.Input();
// List the available ports.
console.log(midi_in.getPorts());
midi_in.openPort(0); // Open the first available port.

// Set a callback to receive the messages.
// This is the generic callback to receive all the messages
midi_in.on("message", ({ message, deltaTime }) => {
  console.log(`Message received at ${deltaTime} : ${message}`);
});

// Stop listening to the event.
midi_in.off("message");

// You can listen to more specific messages.
midi_in.on("note_on", ({ message, deltaTime }) => {
  console.log(`Note on received at ${deltaTime} : ${message}`);
});
midi_in.off("note_on");

// Close the port.
midi_in.closePort();
// It's still possible to open an other port, otherwise you can free the device.
midi_in.freeDevice();

Midi Output

The API is very similar, except you can send MIDI messages.

import { midi } from "https://deno.land/x/deno_midi/mod.ts";

const midi_out = new midi.Output();
console.log(midi_out.getPorts());

midi_out.openPort(0);

// Send a note on.
midi_out.sendMessage([0x90, 0x3C, 0x7F]);
// Can also be sent with a helper class for better readability.
midi_out.sendMessage(new midi.NoteOn({ note: 0x3C, velocity: 0x7F }));
// Send a note off after 1 second.
setTimeout(() => {
  midi_out.sendMessage([0x80, 0x3C, 0x2F]);
  midi_out.sendMessage(new midi.NoteOff({ note: 0x3C, velocity: 0x7F }));
}, 1000);

Complete examples can be found in the examples folder.