The music in the trailer may suggest many things about the upcomming game. For example the note played on the piano at the very start of the trailer and at the end right before, "this is the way the world ends" is said, the exact same note is played on the piano. Perhaps suggesting that the humans will be equal to before the war started. And after that the trumpets, they could signify triumph, but for who the covanent or human kind? Also when the artifact in the video opens up the classic halo battle music start. Could this all mean something?