It came out last week. It comes with four different covers...blatant fan expliotation at its worst... I bought the cover with Liv Tyler on it...which ones did you get?
As for the music in the trailer, I'm not sure, it went by too quickly...besides I've only listened to the whole soundtrack once so far...too busy...and some glitch ate my copy of the trailer so I can't make comparisons...sorry.
Arise, arise, Riders of Theoden!
Fell deed awake: fire and slaughter!
Spear shall be shaken, shields be splintered,
a sword-day, a red-day, ere the sun rises!
Ride now, ride now! Ride to Gondor!
Theoden King: The Return of the King