var WindowObjectReference = null; // global variable

function openMusicPopup()
{
  if(WindowObjectReference == null || WindowObjectReference.closed)
  /* if the pointer to the window object in memory does not exist
     or if such pointer exists but the window was closed */

  {
    WindowObjectReference = window.open("http://www.binglybongly.net/music/music_1.html",
   "music", "toolbar=no,location=no,directories=no,status=no,menubar=no,scrollbars=no,resizable=no,width=310,height=310");
    /* then create it. The new window will be created and
       will be brought on top of any other window. */
  }
  else
  {
    WindowObjectReference.focus();
    /* else the window reference must exist and the window
       is not closed; therefore, we can bring it back on top of any other
       window with the focus() method. There would be no need to re-create
       the window or to reload the referenced resource. */
  };
}