let myFreq = 262;

​

// Variable for Oscillator.

let osc;

​

// Array of frequencies in C Major.

let frequencies = [

  myFreq,

  myFreq * 9/8,

  myFreq * 5/4,

  myFreq * 4/3,

  myFreq * 3/2,

  myFreq * 5/3,

  myFreq * 15/8,

  myFreq * 2

];

​

// Melody Object for C Major

let melody = {name: 'C Major Scale',

              notesIndex: [0, 1, 2, 3, 4, 5, 6, 7],

              tempo: 120

             };

​

// Empty array for oscillator objects.

let oscillators = [];

​

// Calculate duration of each note in seconds.

let noteDuration = 60 / melody.tempo;

​

function setup() {

  createCanvas(400, 400);

  // Initialize oscillators and place in oscillators array.

  for (let freq of frequencies) {

    osc = new p5.Oscillator(freq);

    oscillators.push(osc);

  }

}

​

function draw() {

  background(220);

}

​

// Starts playing the note.

function playNote(n) {

  // Starts oscillator if needed.

  if (oscillators[n].started === false) {

      oscillators[n].start();

      // Starts playing the note by increasing the volume with a 0.01 sec fade-in.

      oscillators[n].amp(1, 0.01);

  }

  // Stops playing the note after noteDuration * 1000 number of seconds 

  setTimeout(stopNote, noteDuration * 1000, n); 

}

​

// Stops playing the note.

function stopNote(n) {

  // Lower oscillator volume to 0.

  oscillators[n].amp(0, 0.01);

  // Stop the oscillator.

  oscillators[n].stop();

}

​

// Plays the notes in a melody.

function play() {

  // Read each [index, note] in melody.notesIndex

  for (let [index, note] of melody.notesIndex.entries()) {

    // Play each note at scheduled time

    setTimeout(playNote, noteDuration * 1000 * index, note);

  }

}

​

// Click on canvas to play the melody

function mousePressed(){

  play();

}