Wired have an
audio interview with John Carmack and Trent Reznor on how Trent's music and sound effects will add to the story of Doom 3. The interview was done last week at E3.
John claims that unlike the full on action-only competition style of game that Quake3 was, Doom3 will be more moody-storyline based with the multiplayer aspect being 'pretty minimal', but Doom3 will not suffer from 'final fantasy syndrome' of endless cut scenes. A lot of the tone of the game will be set not just by the music by the 'eraserhead' style sounds of the environment, which is where Trent kicks in.
Trent says that designing sounds for games is a much different way to create music, and is 'really challenging, rewarding and .. difficult for me'.
The interview's fifteen minutes long, so go check it out if it's your thing.