when track is playing,
      // pause the track and start playing a new src

      _srcChanged: function(oldValue, newValue) {
        var player = this;

        if (player.isPlaying) {
          player._pause();
          player._play();
        }
      },

      //
      // If color property is changed,
      // update all the nodes with the new accent color

      _changeColor: function(newValue) {
        var player = this;
        player.$.left.style.backgroundColor = newValue;
        player.$.title.