http://www.msnbc.com/news/997124.asp
Peter Jackson comments on goofs made in the first two movies of the Lord of the Rings trilogy.
Newsweek: When Arwen and Frodo are being chased on
horseback by the Ringwraiths, the soundtrack to the scene is a
cantering horse. A canter is three beats, whereas a gallop—which is
what the horses on screen are doing—is four very fast beats that
often sound like a single beat.
Jackson: I should’ve—well, it’s
too late to fire anyone. The damage has been done.