Well... there are several ways to play music. There is Theme Music, Music List, Sounds, and 3D Sounds.
The only way I found to make a music repeat over and over, was creating a region, adding the music to that region, check the 'Loop' thing in the Sound Editor, and spread the region across the... area I want the music to be in, and the music will be heard by the player as long as his camera includes the region.
Anoter way could be turning music OFF; and playing the music as a SOUND, with a Loop. Just play it at the Map Init and it should loop over and over. The bad part is that, if player turns off the sounds, will turn of the music too.