$( ".power-switch" ).click(function() {
  $( this ).toggleClass( "off" );
});

var audioContext = new AudioContext();
var oscNode = audioContext.createOscillator();
oscNode.frequency.value = 0;
oscNode.detune.value = 0;
oscNode.type = 'triangle';
oscNode.connect( audioContext.destination );
oscNode.start(0);
var notes = {
  C4:  261.63,
  Db4: 277.18,
  D4:  293.66,
  Eb4: 311.13,
  E4:  329.63,
  F4:  349.23,
  Gb4: 369.99,
  G4:  392.00,
  Ab4: 415.30,
  A4:  440.00,
  Bb4: 466.16,
  B4:  493.88,
  C5:  523.25,
  Db5: 554.37,
  D5:  587.33,
  Eb5: 622.25,
  E5:  659.25,
  F5:  698.46,
  Gb5: 739.99,
  G5:  783.99,
  Ab5: 830.61,
  A5:  880.00,
  Bb5: 932.33,
  B5:  987.77
};
$('.white-key, .black-key').mousedown(function(){
  if ( $("#power").is( ".off" ) ) {
    return false;
  } 
  else {
    oscNode.frequency.value = notes[this.id];
  }
});
$('.white-key, .black-key').mouseup(function(){
  oscNode.frequency.value = 0;
});
$(document.body).on('mouseup, mouseout',function(){
  oscNode.frequency.value = 0;
});