Remove Music while remaining vocals

Okay, the theory of it goes like this; if you have an absolutely identical music track (at the same level as well) - and you can line it up with the one that you want to extract the vocal from - and that alignment has to be sample-accurate or this simply won't work - then you can subtract one from the other and be left with just the vocal.

So what are the chances of being able to achieve this? Let's put it like this; I'm not aware of anybody who's been able to achieve it with any degree of success at all. Even if you have the correct tracks, the sample-accurate alignment is almost impossible to achieve. Incidentally, if you are starting with MP3 files, forget it completely; there are too many decoding errors possible for this ever to work.

If it's a stereo file, then probably the best you will manage is to use Audition's Center Channel Extractor, but this will be far from perfect, as it relies on FFTs to extract just the signal in the center of the stereo field, and this is also prone to errors.

So some result, yes - good result, no, I'm afraid.