let osc;

​

// Middle C frequency. 

let myFreq = 262;

​

function setup() {

  createCanvas(400,400);

​

  // Create an Oscillator object.

  osc = new Oscillator(myFreq);

​

}

​

function draw() {

  background(220);

  // Check if osc is playing.

  if (osc.started === true) {

    // Save frequency of sound.

    let currFreq = osc.getFreq();

    // Set the text style.

    textAlign(CENTER, CENTER);

    textSize(30);

    // Display frequency.

    text(`${currFreq} Hz`, width / 2, height / 2);

  } else {

    // Otherwise display 0 Hz.

    text('0 Hz', width / 2, height / 2);

  }

}

​

function mousePressed() {

   // Toggle the note that is playing. 

  if(osc.started){

    osc.stop();

  } else {

    osc.start();

  }

}

​

​