// create one synth const synthA = new Tone.FMSynth().toDestination(); const synthB = new Tone.FMSynth().toDestination(); //play loop of c6 note every half note const loopA = new Tone.Loop(time => { synthA.triggerAttackRelease("C6", "16n", time); }, "4n").start("4n"); //play g5 every quarter note const loopB = new Tone.Loop(time => { synthB.triggerAttackRelease("G5", "4n", time); }, "4n").start("4n") // the loops start when the Transport is started Tone.Transport.start()