Greetings! I'm pleased to announce that my open-source player for Baldur's Gate music files is now Ogg Vorbis capable and available for general consumption. It can play single .acm files (music snippets), .mus playlist files (playlists of snippets that make a whole song), .wav character soundset files, and even open up BIFF (.bif) archives so you can enjoy the sound effects and ambient sounds.
Oh, and you can export to AIFF if you want to populate iTunes with BG:EE-ey goodness (who wouldn't?).
The source code is up on GitHub at https://github.com/K8TIY/ACMPlayer
Binary for 10.5 and later at http://blugs.com/Downloads/ACMPlayer.zip
P.S. A couple of my personal recommendations:
Baldur's Gate - Enhanced Edition.app/Contents/Resources/music/bc2.mus (my favorite battle music)
Baldur's Gate - Enhanced Edition.app/Contents/Resources/music/nadoys.mus (Adoy's Enclave - gorgeous!)
(if you have it) BG2 SoA/CD3/Data/AREA090A.BIF resource AM0901 (Temple of Helm ambient)