So who is scoring The Passion of the Christ? A report today in Music from the Movies mentions a certain Lisa Gerrard:
Lisa Gerrard to score 'The Passion of the Christ'
Apparently she contributed music to the score of The Gladiator.
Earlier reports suggested that Jack Lenz was to be responsible for the music (e.g. this Catholic Herald report or here from Lenz entertainment). Still earlier reports had suggested James Horner (refuted here at Music from the Movies).