David Dubal: "Mr. Horowitz, which are the most difficult of the Chopin etudes?"
Vladimir Horowitz: "Ah, all are terrible. The double-note etudes are very difficult, especially Op. 25, No. 6. Everyone tries to show off the speed of their thirds, but the beauty of the piece is in the left hand. Of course the thirds have to be played very nice, very evenly. For me, the most difficult of all is the C Major, Op. 10, No. 1. I cannot do that, and I can't do the other C Major, Op. 10, No. 7. Also I can't do the A minor, Op. 10, No. 2. Richter told me he could never do it, either."