In this post by The Mortal Instruments Examiner, we learn that Gabriel Yared, famous for his musical scores for French and American film, will be composing the official score for the City of Bones movie. Cassandra Clare confirmed this on her Tumblr.
Yared’s music tends to have a very exotic, Middle Eastern feel. He actually did the score for a 1998 movie (starring Nicolas Cage and Meg Ryan) called City of Angels! Ironic, right? Listen to some of his work here.