Heh you are completly off probably.
I believe there is some VERY high end software that is used maybe in the broadcast market, I have heard rumors about it never used it myself and i have been doing Audio work for a good while, and all I have seen to show for it is rumors.
How it USED to be done was typically when Vocals were panned dead center in a recording you would take a stereo recording, invert one side of it and summ it to the other, the vocals would be 180 degrees out of phase from each other and would canel itself out, the problem is of course when you have instruments panned dead center, or really just not panned to one side or the other sometimes you get artifacts of them removed and are left with a weird sound
And of course nowadays most pop music DOESNT have the vocals panned dead center
Vocal Removing software does a bit of both(Frequency filtering and phase shifting) I believe nowadays, at least the stuff you find in something like Adobe Audition, which is why it never sounds all that good when you run it through it. At least that is my guess having never really looked at the source code for it for obvious reasons
So what you would in the end want to do is take that track left with the vocal removing software, put it 180 degree out of phase(Invert it if you want to be technical as phase involves time) and sum it with the original track, I make absolutely no garuntees in as far as the quality of the output, in fact i would be willing to be it wont sound all that good, but dont have my software in front of me to check