Special graphics musics exist for the Acorn Lemmings.
A Global Music Pack should be made for this too; you can find them in the same ZIP as the Acorn Lemming musics (http://www.lemmingsforums.net/index.php?topic=1185.msg32541#msg32541).
If they already loop properly, and are in an acceptable format (a module-based format or OGG is recommended, though several others work too) the only thing that needs to be done is popping them into the "musics" folder with the right filenames (beasti, menace, awesome, beastii).