If you mean how to cut the band out of a recording, leaving only the lead singer, I can give you a hint. Only a hint, nothing more, I'm afraid...
The singer is usually panned in the middle of the sound scene. There's several "karaoke" style thingies that can eliminate the center part (=the singer) by splitting the stereo sound and turning the other upside down, so to say. What's panned into the center gets a perfect mirror image of itself, perfectly matching parts of the sound get eliminated by the countersound. This works best with older stereo recordings. Today, the singer's voice is broadened to all over the scene by multiplied takes and echoes, thus making a perfect cutout impossible.
Now your problem is vice versa. It's impossible to cut the band out with the abovementioned way, because the left and right channel are identical only for the center, usually the singer. I don't know if there's any program that can cut out what's far left and right, leaving only the center.
Audacity might be a good (and even better, free
) program to study the matter. It has lots of plugins, from which you might find a suitable tool for your needs.
A nice looking piece of information can be found
here.
Good luck!
