Impossible to take anything completely out of a song.
In studio, it is all seperate tracks, even each drum (and cymbal, depending on the place) are a seperate track.
Once it is mastered, it is all mixed down into one single track.
You can mess with frequencies a bit in your player's EQ... but as far as totally removing something without having the master tracks and hitting the mute switch.... not gonna happen.
From what I understand, the way they do it is using phase cancellation. When 2 sources are 180 degrees out of phase with eachother they cancel eachother out. Ive heard ways to do this but it is very very expensive.
Ive heard of those vocal zapper things, never checked to see if they worked.
Best way, get the original multitrack sessions and just lower the fader.
