a.js

let Chord = (T, noteNumbers) => {
  return T(noteNumbers.map((noteNumber) => {
    frequency: T("mtof", { value: noteNumber }),
  })).T("XLine.ar", { duration: 2, doneAction: 2 });
};

let cmaj = timbre(Chord, [ 60, 64, 69 ]);

cmaj.start(timbre.currentTime).on("ended", () => {
  console.log("END!!");
});

cmaj.connect(timbre.getAudioBus(0));