Hello!
I have a completed grid, but I'm a little unsure about a couple of the changed letters. I can't begin to parse 18a, so that's one of the problems - and I can't see the change in 34a.
As to the end game, I'm only seeing a famous Russian, but I'm guessing from previous responses in this thread that I'm meant to be looking for a musician (and the crossword's title would fit with that). Google isn't helping, so perhaps a nudge on here will...
Suzy x