function addmusic() { 
  if (window != top) {
    var soundurl=parent.frames[1].location.href;
    if (soundurl.indexOf("/sound.html") != -1) {
      document.getElementById('soundcontrol').innerHTML = '<a href="#" id="soundcontrol" onclick="changemusic();">Stop Music</a>';
    } else {
      document.getElementById('soundcontrol').innerHTML = '<a href="#" id="soundcontrol" onclick="changemusic();">Start Music</a>';
    }
  }
}

function changemusic() {
  var date = new Date();
  date.setTime(date.getTime() + (30*24*60*60*1000));
  var soundurl=parent.frames[1].location.href;
  if (soundurl.indexOf("/sound.html") != -1) {
     document.cookie = "sound=off;expires=" + date.toGMTString();
     parent.frames[1].location.href = 'nosound.html';
     document.getElementById('soundcontrol').innerHTML = 'Start Music';
   } else {
     document.cookie = "sound=on;expires=" + date.toGMTString();
     parent.frames[1].location.href = 'sound.html';
     document.getElementById('soundcontrol').innerHTML = 'Stop Music';
   }
}