OMF:BG's dynamic music system is actually not that bad as it makes sure not to cycle to a different tune section until the previous one is concluded, so at least it sounds consistent. Descent 3 has a similar music system that's timed to schedule changes from event triggers, either time-based or map-position based.
Magic Carpet and Magic Carpet 2 are interesting in that each tune has two flavours, a peaceful one and a combat one, both playing in sync but one is always faded out while the other runs, and they fade between each other depending on if the player is taking damage or not.
System Shock's music system is... odd... I've never been able to quite figure out what exactly it's doing as whole music pieces appear and disappear based on certain areas and it sometimes feels like it's glitching out rather than being dynamic. :P
--- Kris Asick (Gemini)
--- Pixelmusement Website: www.pixelships.com
--- Ancient DOS Games Webshow: www.pixelships.com/adg