''It has the reputation of being the single most difficult piece in the world," said Ledbetter. ''It is so difficult that the composer himself couldn't play it."
I'm not sure I'd say it's the "single" most difficult piece, it is wildly difficult and not very rewarding as music goes, but I wonder what is the single most difficult work for piano. I imagine it has no real answer. It's likely that its whatever happens to be sitting on your music desk at this moment. Whoever you are, wherever you are in your journey playing the piano.