Dec 20, 2005 — 8:10:22 PM
The problem with live singing, is that you have to be even more careful with keeping everything else on and around the set, quiet. It has been done, but very rarely, and never when there is much action happening. The are too many cuts (stops and starts) in filming, and to ensure a perfect match in vocal, it is just best for the actor to sync to a recording. They rarely, if ever, dub the vocal after it's been filmed. They always are syncing to a pre-recorded vocal.