Free are only able to have embedded audio/video files place on the site. Gold, Sliver, and Bronze sites support MP3 and RealAudio file formats.
*Tip: When selecting a file for your background music, consider the size of the music file and the number of visitors that page gets. This is important because bandwidth used by the background music of your web pages can very quickly add up to a lot of bandwidth. When a song is setup as background music it will be played every time someone visits that page. So, if the music file is an mp3 that is 5MB in size, up to 5MB of your hosting packages bandwidth will be used every time someone views that page. If you have 1000 visitors in a month, that could add up to 5GB of bandwidth.