Tone.js app - audio won't start until second click

Question

I'm aware that I need a user action to start Web Audio on mobile. However I have followed the recommendation to resume (in the case of Tone.js call Tone.start()) on user action but it still don't work. Here are the relevant parts of my code:

keyElement.addEventListener("touchstart", notePressed, false);
keyElement.addEventListener("touchend", noteReleased, false);

function notePressed(event) {
        let dataset = event.target.dataset;
        if (!dataset["pressed"]) {
            let octave = +dataset["octave"];
            oscList[octave][dataset["note"]] = playTone(dataset["frequency"]);
            dataset["pressed"] = "yes";
        }
        event.preventDefault(); event.stopPropagation();
    }
function noteReleased(event) {
      let dataset = event.target.dataset;

      if (dataset && dataset["pressed"]) {
        let octave = +dataset["octave"];
        oscList[octave][dataset["note"]].triggerRelease();
        delete oscList[octave][dataset["note"]];
        delete dataset["pressed"];
      }
    } 
function playTone(freq) {
        let synth = new Tone.Synth().toDestination();
        let now = Tone.now();
        Tone.start();
        synth.triggerAttack(freq, now);
        return synth;
    } 

It works fine on the second touch, but after the first touch I get a warning about the audio context being suspended, even though the standard is that it is resumed when start() is called by a user action. I'm stumped here.

Answer 1

That Tone code looks correct. I simplified it in a CodePen and it worked on mobile on first click (iOS).

var keyElement = document.getElementById("play");

keyElement.addEventListener("touchstart", notePressed, false);
keyElement.addEventListener("touchend", noteReleased, false);

// Added mouse ELs to test on non-mobile.
keyElement.addEventListener("mousedown", notePressed, false); 
keyElement.addEventListener("mouseup", noteReleased, false);

var pressedTone;

function notePressed(event) {
  console.log("notePressed");
  pressedTone = playTone(440);
  event.preventDefault();
  event.stopPropagation();
}
function noteReleased(event) {
  pressedTone.triggerRelease();
}
function playTone(freq) {
  console.log("playTone", freq);
  let synth = new Tone.Synth().toDestination();
  let now = Tone.now();
  Tone.start();
  synth.triggerAttack(freq, now);
  return synth;
}

Here's the link to the CodePen: https://codepen.io/joeweiss/pen/gOmeQVW