With regards to the moral issues / actually getting surfers to your site more than once:
How about a 2-frame page, 5% / 95% split. Top frame contains "You are listening to MySong by Me. Press here to Shut the **** up" - that way they have the option to stop it. This would probably entail having the onload call a js to play the music, and the js checks then enabled tag to see if it is allowed to play. Then the link (or button) in the header frame kills the enable tag.
If you want to get really tricky, you could put audio player controls in the header frame - play / pause / stop / next song / previous song / volume up & down.....
Now there's a project for ya!