Embed Src question

Why i can't change the src of the embed player to play another song...
How to do when i select a value on the dropdown menu to change the src of the embed player ?


   Music Player :
   <br />
    <select name="musiclist" onchange="javascript:MusicChange(this);">
     <optgroup label="WMA">
      <option value="WMA-1"> Unknown </option>
     </optgroup>
     <optgroup label="MP3">
      <option value="MP3-1"> The Reason </option>
     </optgroup>
     <optgroup label="MIDI">
      <option value="Midi-1.mid" selected> Midi-1 </option>
      <option value="Midi-2.mid"> Midi-2 </option>
      <option value="Midi-3.mid"> Midi-3 </option>
     </optgroup>
    </select>
   <br />
    <embed name="musicplayer" src="gallery/audio/midi-1.mid" width="120" height="45" hidden="false" autostart="true" loop="true">


<script language="javascript">

function MusicChange(list)
  {
   document.musicplayer.src = "gallery/audio/" + list.value;
  }

</script>