As of today, the game is capable of playing Ogg Vorbis audio files. That's it.
In the long run, what is planned is to support Csound which would allow very cool effects, such as dynamically changing the music while the game is running, typically following the action. If there's a lot of fight, the music could reflect this.
For now this is only vaporware, just a nice idea among others, nothing implmented yet.