johanibraaten
Hi David.
First, what a fortune to be able to work on "Pictures at an exhibition", It's such a masterpiece. I was lucky enough to see it live last autumn with the Ukrainian pianist Anna Fedorova, it was a marvelous experience.
I don't know if I can contribute with anything meaningful here but as others have mentioned, the difficulties to memorize this music has most certainly to do with the music itself. There is these repeated themes, specifically the "promenade" theme that repeats itself constantly in new shape and forms which is seemingly very easy to get mixed up. And the structure of the music is also quite "loose" as program music like this often is which, at least for me, makes it harder to remember. When I'm working with a memorization process I find it helpful to work with the music in multiple ways. In this case I think it would be helpful for me to make a structural and harmonic analysis of the music both at, but also without the piano in writing. Maybe in this case I also would find it useful to listen to Ravels orchestra version, perhaps the different instrument colors could benefit the memorization process and be something to refer to. I hope you don't mind me asking but why do you think your professor wouldn't understand? To me this is one of the most normal challenges that are presented to a music student. Anyway this is only my two cents and I'm pretty sure you will sort it out.