Isolating instrumentals

I have tried to nut this out using maths taking account of the fact inverting creates a “negative” sound but to no avail, so I thought I’d ask here for ideas. I have two tracks which are identical (bar tiny differences which do not bother me due to mp3 encoding) except for the vocals - and I am trying to isolate the instrumentals. Anyone have an idea about how to do this? I know there are various centre pan removers and such but I thought there might be a way to take advantage of this “redundancy” - somehow find which audio is the same.

To put the tracks simply:
track 1: instrumentals + vocal 1
track 2: instrumentals + vocal 2

Any help would be appreciated - thanks in advance!

First, a word of warning: these inversion tricks only rarely work the way people expect, and very often don’t work at all.

They are based on the fact that if you have two tracks (say the L and R tracks of a stereo recording which you have split into two mono tracks), and you invert one of them, you cancel out the parts that are the same in both tracks, and leave the rest. If the vocals are dead centre and the instruments are panned to the sides, the vocals will cancel, leaving the instruments. However, any instruments panned to the centre will also be lost.
If the vocals are not dead centre, or if there are echo or reverb effects added, it won’t work.

In your case, I assume you have two stereo tracks, which complicates the problem even more. but it comes down to the same thing; there is no advantage in having two tracks with the instrumentals the same. if the instrumentals in the two tracks are exactly the same, (and I mean bit-for-bit identical) and you invert one track, you will get the following:

(Inst + vocal 1) + (-inst -vocal 2), which equals
vocal 1 + (-vocal 2), i.e. both vocals.

If the instrumental parts are not exactly the same, (and it appears from your description that they are not) you will get a ghost of the instrumental along with the vocals.

If your two tracks are both stereo tracks, your best bet is to try the Vocal Remover on each of them separately. If you are one of the lucky ones, it might work on one of them.