As far as I know, and that is certainly not much, Ravel wrote 2 piano concertos. Both are fantastic, and contrast nicely with each other. They were both written around the same time, 1929-1930. The Concerto in G is light, jazzy and has an affecting adagio in the middle section. The Left Hand Concerto is dark and moody and doesn’t have a middle section.
The Left Hand Concerto was commissioned by Austrian pianist Paul Wittgenstein, who happened to be the older brother of Ludwig Wittgenstein, the famed philosopher (known for quotes such as “I don’t know why we are here, but I’m pretty sure that it is not in order to enjoy ourselves.”). Anyhow, Paul Wittgenstein made his musical debut in 1913, at around age 25. In 1914, World War I breaks out and he is called into Military Service. It does not go well for Wittgenstein, during a battle he is shot in his right arm and then captured by the Russians. His right arm is amputated. While recovering in a prisoner of war camp in Siberia, he resolves to continue his career as a pianist using only his left hand. After the war, after much study, he approaches many well-known composers of the day, including Maurice Ravel who wrote the Piano Concerto for the Left Hand for Wittgenstein. There was friction between Wittgenstein and Ravel, after Wittgenstein made changes to Ravel’s score. Go figure.