In my experience removing vocals from a song rarely works satisfactorily.
The usual technique relies on the vocal being in the center of the stereo mix, and the instrumentation panned left and right. The theory is that you strip out the center and are left with a karaoke version.
Problem is that virtually no tracks are recorded like this! Older records did often hard pan the band to all parts of the stereo space, but thanks to the loudness wars that isn't often the case any more… after all you only get half the volume on your drums if they are only coming out of one speaker! And louder is always better
Even if the original panning is a well defined as it would need to be for the technique to work well, as soon as you add any sort of reverb to the mix this blurs all the sounds, pushing the echos all over the place, such that when the center is removed you still hear the ghost of the original bouncing around.
All this can be controlled to a degree by filtering out the various frequencies where the vocal used to be, but since the human voice covers such a wide range of the spectrum, you will end up with a very muffled sound.
If there isn't an instrumental version of the track you are after in existance, then the only good solution I've ever found is to rebuild the track by sampling, looping and reconstructing major sections of the song. Have done this several times as paid work for TV and theatre, but it is difficult and time consuming.
Also consider finding a midi version and putting it through a really good soundfont, or even splitting it out to various virtual instruments.
