Hey look, it's Two Steps From Hell again!
Sounds like two or three songs, possibly two merged at one point.
Also, it looks just like the Gears of War and Halo trailers - tug on the heartstrings affairs with a troubling emphasis on Earth. I played Mass Effect as a citizen of the galaxy; why should Earth be more important to me than the Citadel? Why would my Shepherd care?
This trailer, and all the marketing, seems to assume that the player will automatically care about this sudden threat to Earth, but why do the Reapers even care? Some sort of blood feud? And anyway, there's much better things to do than take back Earth from a swarm of distracted intergalactic robots (hey, wanna bet an EMP weapon of some sort ends up being instrumental? Kill all the reapers, at the cost of regressing galactic civilization to a Stone Age level?) who would not be focusing on my actions and objectives taken in, y'know, actually defeating the bloody things!