I came across a couple of VST audio plug-ins for removing or isolating vocals in stereo music that you may not have known about. One is called Extra Boy Pro and the other is called Voice Trap. There don't seem to be too many of these plug-ins in my price range that both remove or isolate vocals with the capabilities that these plug-ins have. There's another plug-in from iZotope that you get with Sony Sound Forge Audio Studio 9.0 that does both, but you have to spend about $50 to get the full version of Audio Studio that has that plug-in enabled. My version that I got for free with Sony Video Studio and DVD Architect Studio does not have the plug-in enabled.
The best sounding results come from Extra Boy Pro, IMO, but both are very interesting and fun to play with. Both VST plug-ins work in Sony Sound Forge Audio Studio 9.0. I also have them working in Premiere Elements 8.0. They probably work in most applications that accept VST audio plug-ins.
I have a Dusty Springfield song that only Extra Boy Pro could isolate the vocals. I drew a rectangle on a 2D image of a spectogram to isolate the vocals. But then there are times when only Voice Trap will do the job. For removing vocals, sometimes the plug-in that comes with Band-in-a-box works just as well, or better.
It's kind of rare that you have a song where you can completely eliminate vocals or completly isolate them. So that's kind of the fun and challenging part, to see how close you can get.
Voice Trap V2.0
http://www.cloneensemble.com/vt_main.htm
$25 USD
Elevayta Extra Boy Pro
http://www.elevayta.net/product14.htm
$29.95 USD