Having spent five days recording five Beethoven sonatas and two concertos, Schnabel wrote to his wife:

This week was an ordeal, a torture chamber. “What does not kill me makes me stronger,” says Nietzsche. Hopefully (probably) this is true. I had no idea of how outrageous a process the recording on discs could be. Like slave drivers they burdened me with six hours of recording on a daily basis. I had to play pieces that were not included in the contract, but I had no time to prepare them. They thought I was always able to play all the Beethoven sonatas and concertos at the drop of a hat. Instead of refusing to do anything that was not prearranged, I let them, as usual, cajole me into doing it…. The act of violence against humans is mainly caused by the imperfection of the machine, which he has created. For example: one can only play for four minutes. In these four minutes sometimes 2000 or more keys are hit. If two of them are unsatisfactory you have to repeat all of the 2000. In the repeat the first faulty notes are corrected but two others are not satisfactory, so you must play all 2000 once again. You do it ten times, always with a sword of Damocles over your head. Finally you give up and 20 bad notes are left in it. I am physically and mentally too weak for this process and was close to a breakdown. I began to cry when I was alone in the street. Never before had I felt deeper loneliness. My conscience tortured me. Succumbing to evil, the betrayal of life, the marriage by death. It is perfect nonsense, totally unnatural. Depravity….

Artur Schnabel, in a letter to his wife, Therese, 26 March 1932. Cited in: James Irsay, “The Complete Beethoven Piano Sonatas–Artur Schnabel”, https://www.loc.gov/static/programs/national-recording-preservation-board/documents/SchnabelBeethovenPianoSonatas.pdf, accessed 19 August 2020.