This sort of stuff at bar 33 – squashed flies on a page – happens all over Chopin. One moment everything’s calm, the next the right hand is fitting in millions of notes for every note in the LH. Well, not millions, but enough for the little black dots to blur in front of the eyes and beads of sweat to form on the forehead. Four per note for the first three beats. And then – count them – eighteen for the next three. Six a beat, strictly speaking, except that would sound rather mechanical. So perhaps split them six-eight-four? They have to sound effortless. But that means a long time with a pencil writing in exactly which finger is going to play which note and then memorising it all.