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                <h1>Web MIDI Starter</h1>

<button id="sendMIDIMessage">Send MIDI Message</button>


                body {


                  const MIDIOutputs = [],
        MIDIInputs = [];
  // Handle incoming MIDI messages
  const handleMIDIMessage = (event) => {
    data =;
    // do more interesting things here!
  // Cycle through connected controllers and attach incoming MIDI message listener
  const onMIDIInit = (MIDIAcessObject) => {
    // iterate through all the outputs and store in an array
    for (let output of MIDIAcessObject.outputs.values()) {
      console.log(`Found output: ${}`)
    // iterate through all the inputs and store them in an array
    for (let input of MIDIAcessObject.inputs.values()) {
      console.log(`Found input: ${}`)
      // attach an event listener for incoming MIDI messages
      input.onmidimessage = handleMIDIMessage;
  // In case things fail...
  onMIDIFail= function(){
    console.log("Could not load MIDI");
  // Request access from the browser
  navigator.requestMIDIAccess({}).then( onMIDIInit, onMIDIFail );

  When the button is clicked send a MIDI C3 "noteOn" mesage to channel 1 on the first MIDI device stored in our MIDIControllers array
  document.querySelector('#sendMIDIMessage').addEventListener('click', (e) => {
    MIDIOutputs[0].send([144, 63, 127]);