<EMBED SRC="<name of your sound file>" height=2 width=2 autostart=true hidden=true>
For example, let's say you want to play a wave (*.WAV) file called hello.wav in the background. All you have to do is insert the following tag in between your <BODY> and </BODY> tags:
<EMBED SRC="hello.wav" height=2 width=2 autostart=true hidden=true>