Basically any song or piece of music produced after 1923 is still in copyright. If you place any music composed or written after this date in any form, even if you include music only versions in midi or wav file forms, you are in infringement of copyright.
Where you aware recording songs of TV or Radio is illegal? Well it is and the same applies for internet . The law also doesn?t differentiate between personal sites or commercial sites, and in this climate of music industry getting more and more protective over their copyrights, more and more people are getting sued, even personal sites who make no money. You are still using their music without permission and broadcasting it without a licence.
If you want to cover yourself you can write to the copyright holder and ask permission. Or if you have just won the lottery you can pay the broadcasting fees and pay a fee every time your file is downloaded or played! Not very practical.
From design point of view why are you putting music on your site. You may think its most wonderful piece ever but the visitor may not. Its ok to have music on your personal site, but music or sound is not a good idea for non personal sites, like commercial or information sites.
Hearing same piece of music can grate on peoples nerves and they will soon click off your site. Also most people who visit website do so from work . most of these people work in open plan offices and have fixed speakers with no sound control etc, so as soon as they load your site and a blast of sound emits from it they will kill the page as fast as they can not wanting to attract attention from their boss.
Best way to have music on your site is to have a ?click here to play my favourite music? button so they can play your song if they want to. That way people aren?t going to kill your page as soon as they hear the first note.
Hope this is of help