Not sure. Might use one from my sound guy, or I might find a song specifically for the trailer.Well by the time most devs make trailers they probably have finished all/most of the game with just polishing left for the most part.
I don't actually know a lot about how big devs make trailers. Closer to release you can just film stuff, but for early trailers are they making a bunch of little vertical slices similar to demos?