Hi xoom,
I'd like to say they're a multitude of sins regarding this, but there are probably only a couple. The following code was used in an old website of mine for midi files (with a little manipulation this may be your answer, if not it may be a start).
CODE
<script TYPE="text/javascript">
var filename="engelrammstein.mid";
if (navigator.appName == "Microsoft Internet Explorer")
document.writeln ('<BGSOUND SRC="' + filename + '" LOOP="INFINITE" VOLUME="-800">');
else if (navigator.appName == "Netscape")
document.writeln ('<EMBED SRC="' + filename + '" AUTOSTART=TRUE HIDDEN=TRUE LOOP=TRUE VOLUME=80><P>');
</SCRIPT>
<!-- <NOSCRIPT><BGSOUND SRC="engelrammstein.mid"></NOSCRIPT> -->
This code was written a long time ago as it appeared to me that different browsers handled things differently (of course keep in mind as well that I'm not proficient in writing web page codification(s), but I'm learning validity) and the web that this script resides in is still
online until later this year.
Hope this helps you in the right direction.