Right now I'm trying to learn the 6-Part Ricercar from the Musical Offering. Which is a quite thorny piece, and makes me realize that I really don't understand the process of how music gets into my fingers. I'm not memorizing it, and it seems like there are too many notes / fingering decisions for me to be able to parse it, even with annotations, but somehow I'm learning the piece anyways.

How much of that is muscle memory? I'm sure that auditory memory is quite important, but I don't understand the mechanism: does auditory memory help with muscle memory, does it improve my ability to parse, it that reduce my need to parse, does it help in other ways?

Amazing piece. As is the 3-Part Ricercar: there, my brain has gone through a phase transition after I've gotten it into my fingers where I can pick out the voices much much better than I'd been able to before, hugely improving my options when interpreting the piece. If I can get to that state with the 6-Part Ricercar, it will feel wonderful.