I just did the Maw recently and for the second time the music messed up. When I drove the Warthog for the first half it played the sad women chorus (Don’t know the title) instead of the other song and when the second part came the chorus was playing with the main theme?! Not only does it happen as I’m playing, but continues to play throughout the ending cutscene. I don’t recall this ever happening with my first playthrough so why would it happen now?
It’s a glitch. Sometimes it happens, and sometimes it doesn’t. Sucks though.