JSFiddle - React, Tailwind, and code Playground

JavaScript

let audioCtx = new AudioContext(); 

let osc1 = audioCtx.createOscillator();
let osc2 = audioCtx.createOscillator();
let gain1 = audioCtx.createGain();

let osc3 = audioCtx.createOscillator();
let osc4 = audioCtx.createOscillator();
let gain2 = audioCtx.createGain();

let osc5 = audioCtx.createOscillator();
let osc6 = audioCtx.createOscillator();
let gain3 = audioCtx.createGain();

let masterGain = audioCtx.createGain();

osc1.frequency.value = 330;
osc2.frequency.value = 330.2;
gain1.gain.value = 0.5;

osc3.frequency.value = 440;
osc4.frequency.value = 440.33;
gain2.gain.value = 0.5;

osc5.frequency.value = 587;
osc6.frequency.value = 587.25;
gain3.gain.value = 0.5;

masterGain.gain.value = 0.5;

osc1.connect(gain1);
osc2.connect(gain1);
gain1.connect(masterGain);

osc3.connect(gain2);
osc4.connect(gain2);
gain2.connect(masterGain);

osc5.connect(gain3);
osc6.connect(gain3);
gain3.connect(masterGain);

masterGain.connect(audioCtx.destination);

osc1.start();
osc2.start();
osc3.start();
osc4.start();
osc5.start();
osc6.start();