I remember seeing something like this in VirtualDJ the last time I fired it up and updated a few years ago. Only noticed because they'd remapped the high/mid/low EQ knobs on my old Numark controller to remove bass, drums, vox, etc.

Wasn't what I was looking for initially but it was surprisingly good compared to the older "vocal remover" type plugins I remember having for Winamp et al back in the day. If I ever actually DJed anymore it would definitely be useful for mixing tracks.