Hi BlackReef

Obviously copyright is one problem. Lets assume your client owns the copyright.

you can use frames to do this. but this means using frames on the whole site. You would just load an MP3 player (such as Flash) into the 1 px frame at the top of each screen.

I'm not so sure about the hidden popup approach though it is basically the same principal. You could try googling for 'hidden popup'. I think frames are better a) because there is no problem with popups being blocked b) Google Adwords (if your client is using this) doesn't like hidden popups on a landing page and c) in your case if your client wants controls I think this will be easier to implement using frames. If you want to keep it really simple you could have the controls in the same frame as the Flash (or other MP3) player.

So my suggestion would be to do a simple frameset with the flash player and some controls for it as a thin frame - say at the top or footer depending on the design of the site

Of course you will still need to work out how to do a) frames and b) a simple Flash page