How can I separate the vocals from an audio track during mixing?

I would like to be able to take out the vocals from a song and be able to either use those vocals over a mixed in song or use the instrumentation for an accapella. Is it possible?

Not with MP3 files. Native Instruments has introduced STEEM Files. With Traktor Pro 2 it is possible. But there are not many artists who support this new File format.

The only way is to use the EQ to reduce the Volume of Mid Frequencies where the Voice is for mixing.