Need help

If you find Midi files and have some program like Logic or Cubase or something, you will probably be able to.
 
I've seen some, most of them are based on removing the common between the two channels. Vocals are generally mixed full on both channels so it works, but quite frankly it starts sounding like utter crap BEFORE you could get rid of the vocals.

They're useful for LOWERING the vocals', though it depends on the recording.