Music in Doms 3 is superb.

[B0rsuk]

Wait, so you actually get more music in full version ?
Is there any chance of getting Dead Can Dance in a patch ? With Luck Scale:3 ?

As for music in games, there are some very good reasons to make new music. There are basically two kinds of game music:

- durable music
- story music

Durable music is often underrated, but if done properly, it's great for RTS, TBS, FPP and other 'long' games. The point is that some music, while quite good, gets annoying after a while. Music in strategy games mustn't be annoying after a while.
Just because a piece is good doesn't mean it would work in a game. House of the Rising Sun (The Doors) or Smoke On The Water (Deep Purple) are nice pieces, but you wouldn't survive long exposure without getting Insane afliction.

Story music - generally has shorter life than durable music, and is tailored exactly to needs/situation. Best example would be Planescape:Torment. Really great music, but you wouldn't want to listen to (most of) it in loops.