Many thanks to Total Audio's Marty O'Donnell, who left a few tantilizing hints regarding the state of music in Halo via a forum post. An except for those of you who fear WebBBS:

Don't worry, there will be plenty of places in Halo for music to burrow deep into your soul and get you feeling what you need to feel.

Halo just keeps getting more and more appealing, doesn't it? Methinks it's time to add a music section to the FAQ to keep up on the subject.