343 announced earlier today that Neil Davidge (probably best known for his contributions to Massive Attack) will be composing the official soundtrack for Halo 4. They also released a short sample of the game's music:
Thoughts? I had never heard of this guy before today and I don't envy anyone who has to follow in Marty O'Donnell's footsteps, but that sample sounded great. Different from the tone and style of previous Halo music, but it still fits the franchise well IMO.