That's exactly what I was going to say, or something like it.
Removing vocals in this way is just letting the center phase out, and it's sometimes called "A minus B", and you can do it with speakers as well, by reversing the phase.
If there are any backup vocals panned Left and Right, then you won't filter those out. Lead vocals are usually panned up the center, but reverb is usually wide. So if there was reverb mixed on the vocals, then you won't get rid of that either. But you will get rid of the sample's kick drum and snare drum if there is one, and bass guitar, as those are usually panned center as well.
The faders must be at exactly the same level for this to work, as sine waves are additive, and you need exactly the same amount of Left information from Right information.
We did this in class with "Billie Jean" and it was funny as hell listening to Michael's backup vocals alone, along with some crazy reverb and keys and guitars without most of the drums. Try it: it's funny. I have done it with an mp3, but it didn't work as well.