http://wiki.frictionalgames.com/hpl2/amn..._functions
void PlayMusic(string& asMusicFile, bool abLoop, float afVolume, float afFadeTime, int alPrio, bool abResume);
Plays music.
asMusicFile - the music to play + extension .ogg
abLoop - determines whether a music track should loop
afVolume - volume of the music
afFadeTime - time in seconds until music reaches full volume
alPrio - priority of the music. Note that only the music with the highest priority can be heard! 0 - highest, 1 - lower, etc
void StopMusic(float afFadeTime, int alPrio);
Stops music.
afFadeTime - time in seconds until music stops
alPrio - the priority of the music that should stop
Place play music in OnEnter, and place stop music in OnExit