fincs comes up with an early, proof of concept, SSEQ player. SSEQ is the official music format used in Nintendo DS games. As distributing a ROM with copyrighted music would be a copyright infringement, you can only get the sources for the player routine for now.

You can discuss about the player here, at the GBAdev.org board.

http://fincs.drunkencoders.com/2011/06/26/homebrew-sseq-player/