Do you guys know the story? Rachmaninoff was so sick of his Prelude in C Sharp Minor overplayed in encores. His student was excited that Rachmaninoff came to his concert, he told that he plans to play Prelude in C Sharp Minor for an encore. Rachmaninoff said "if you play it, I'll leave". The concert was successful, the student was excited to launch his Encore. He proudly strikes A, and G#, and saw a big guy stands up in the audience, so from that C#, he switched to Chopin Impromptu No. 4.