Sending MIDI

MIDIOutput.send(data, timestamp?) accepts a number[] or Uint8Array of raw MIDI bytes and an optional send timestamp in milliseconds (performance.now() domain).

Basic sends

import { requestMIDIAccess } from "react-native-midi-api";

const midi = await requestMIDIAccess();
const output = [...midi.outputs.values()][0];

if (!output) {
  console.warn("No MIDI output connected");
  return;
}

// Note On — channel 1, note 64 (E4), velocity 100.
output.send([0x90, 64, 100]);

// Note Off — same note, velocity 0.
output.send([0x80, 64, 0]);

// Control Change — channel 1, CC 7 (volume), value 127.
output.send([0xb0, 7, 127]);

// Program Change — channel 1, patch 0.
output.send([0xc0, 0]);

Scheduled / timestamped sends

Pass performance.now() + offsetMs as the second argument to schedule delivery:

const now = performance.now();

// Note On immediately.
output.send([0x90, 60, 127], now);

// Note Off 1 second later.
output.send([0x80, 60, 0], now + 1000);

Clearing the send queue

output.clear() discards all pending scheduled messages:

output.clear();

SysEx sends

SysEx requires { sysex: true } at access time — see the SysEx guide.