Paul, older brother of philosopher Ludwig, lost an arm in WW1 and then commissioned composers to write left-hand only pieces for him. By all accounts a temperamental character, he torqued several now-great names while simultaneously enriching the repertoire through his sponsorships.
Melissa Lesnie‘s article “The Man with the Golden Arm” is fascinating reading.
Here is Wittgenstein at the keyboard with Bruno Walter and the Royal Concertgebouw Orchestra in Ravel’s Piano Concerto for the Left Hand.