For pianists:Which is the most difficult piece of music to play for you at the p

Question:

For pianists:Which is the most difficult piece of music to play for you at the piano ?

There are lots of hard pieces but some insist that Rachmaninof's are the hardest...

Best Answer - Chosen by Asker: Franz Liszt Hungarian Rhapsodies especially No3
Beethoven Appassionata Piano Concerto (First Movement)

Rachmaninof Piano Concerto No3 is by no means the hardest technically, however the film Shine depicts it as a difficult piece emotionally which it is.

The speed and amount of notes in a piece doesn't always mean it's harder than a slower piece. I think if someone can play a slow piece such as the Moonlight Sonata well it shows a deep understanding and knowledge of the piano as it's harder to delay playing a note and play it soft than to play it qick and loud.