Jay Barbeau was the original composer - clearly incredibly talented. He has part of the original soundtrack for purchase on Amazon (
here) - unfortunately, it doesn't include the tune for Kelethin, which is also my absolute favorite in the game. I really wish someone would do a skillful cover of these with real instruments (trumpets, harp, and so forth).
Engaget
did an article on the soundtrack. It truly is one of the best parts of the game.