The prize came for work including Charlie Wilson's War, Michael Clayton and I Am Legend.
The best original score honour went to Dario Marianelli for Atonement, while Marc Streitenfeld was the Academy's new discovery with his score for American Gangster.
Angelo Badalamenti received a Lifetime Achievement Award at the event which was presented by Marianne Faithfull.
After the eremony the Brussels Philharmonic conducted by Dirk Brosse performed music for composers including Badalamenti and Marianelli.
Special guests of the evening were Siouxsie Sioux and Beth Rowley, both singing music of The Edge of Love.