<OBJECT ID="Player"
width="500" height="500"
CLASSID="CLSID:22d6f312-b0f6-11d0-94ab-0080c74c7e95">
<PARAM name="autoStart" value="True">
<PARAM name="filename" value="http://www.geocities.co.jp/jjmahhk06/songs01/01.mp3">
<embed src="http://www.geocities.co.jp/jjmahhk06/songs01/01.mp3" autostart="0" type="video/x-ms-wmv" width="500" height="500"></embed>
</OBJECT>
Note if the source audio link is invalid, the player might not show up in Firefox. And I think sometimes it is not straight forward to embed WMP in Firefox. Why don't you try it out and let us know what you found?