Complicated. It has to be uploaded to the Web somewhere; do you have a space where you can upload music files?

I don't know anything about this place, just searched for it:

http://www.4shared.com/share_music.jsp

But someplace like that if you don't have your own Web space (I do) that allows you to share music.
<embed src="http://margomcphillips.com/stuff/NEVEREND.MID" autostart="false" width="200" height="100"></embed>
(press the little arrow (second from left) next to the little sound button, twice)

Then if you know how to use HTML to make a little player, you can do that with the "embed src" command (see http://www.pageresource.com/html/embed.htm ) like I did here, (theme from the movie, Neverending Story) or you can just link to it like you would with any other URL (just paste it into the post) and it will go to the URL/site where you've uploaded it and play.