Separate vocals from vocal samples in instrumental

[konsszti]

Hey all,
I recently ran into the problem of seperating the vocals of "O superman" by Laurie Anderson from the instrumental. I think the software got confused which is which, because the instrumental is basically a looped vocoder recording of Laurie Anderson singing :" ah ah ah ah..." The vocals are also with vocoder so quite hard to distinguish...
I know very specific but does anyone here maybe have a tip or suggestion on models, settings etc. on how to solve this?