Marty O'Donnell has been interviewed by Electronic Gaming Monthly; the three-page article is online at 1Up.com. Fun fact: Halo 2 has about 15,000 lines of random combat dialogue. So far.

While most of Bungie has been mum lately about the single player campaign, Marty does reiterate how his sound work is contributing to it, and what Bungie is trying to do in the second game:

I think if you look at what we're trying to do with Halo 2 in the story is that we're trying to make the aliens more fleshed out, rather than just targets/cardboard cutouts. The Covenant is a collection of alien races that have come together for very strong religious purposes, and we wanted to make sure that people understand that this is a long, long history of cultures that have come together for a reason. There's something real there. So we spent a lot of time on fleshing out the alien races. Joe Staten will be back as a grunt, because he was sort of beloved, but let me just say that we've fleshed out the alien races quite a bit. There are more voice actors involved.

As a natural follow-up, EGM asks if Elites still speak in backwards English-- a question Marty won't answer.