This Toccata and Fugue has been the hardest thing I have ever played. It runs for over 8 minutes, all nonstop running passages and intertwined voices. The difficulty of the polyphony in this fugue makes every other bach piece I have ever played seem like child's play. (I'll post the whole thing later)
It was a mental challenge, as learning and memorizing the entire thing took me over an entire semester. Compare to that that I learnt Chopin's minute waltz in a few days (Which I'll also put on youtube if anyone wants to hear that)
It's also a physical challenge, because the polyphony requires me to constantly play 2 things in one hand, resulting in odd hand shapes and stretches. And finally, I have to make sense of it, and not just play notes, but try to bring out the incredible ammount of details in the piece, starting with all the introductions of the theme.
I'm glad you all can appreciate it!