I think George has a point here. The way vocals are removed is not an exact science. It is instead a pot luck processing that hopefully removes most of the vocals. And if the vocals were recorded dead center pan then that process will work pretty good but, never without removing some background music also.
The way I understand it also is that you will get a better result if vocals were recorded center pan and all other music is recorder off center one way or the other. Could be wrong.
Just chimming in here.
Wally
