If you wish to play the mp3s on the website, you need to use other systems such as flash players or html5. Make sure that the mp3s you upload are yours (you own the copyright or have a formal, official, legal right to use them in such fashion).
a great alternative to adding embedded music is from a company called grooveshark.com they have a lot of lisenced music where you can add embedded play lists.
to those that are unfamiliar with it
its basicly a service were you can listen and add playlists and add music to your favorites completely free if you want to buy the music you pay for it. seems like a legitimate service to me and unlimited amounts of music.