Backing tracks

Hi and welcome
If you have the original track and the acapella, in theory you could make an instrumental using phase inversion;
Invert the phase of the pella to cancel the vocal from the original.
Phase inversion is like throwing 2 equal stones at each other, if both are the same and are thrown at each other
at the same speed they will cancel each others momentum.
Unfortunately.. mainly due to mastering, this theory doesnt always work out as mastering will change 1 of the ‘stones’

(I should teach this stuff hehe )