Here we are on the exercise no.19. It is a three four allegretto, having no particular difficulties except for some measures (as the fourth one) during which left hand stands to make room for the right one, in the meanwhile playing a staccato.
The exercise no.20 is supposed to be a bit bothersome, because of the time: in fact, on the down beat of the fourth movement in every measure, after playing a three movements note, the right hand will make room for a note of one movement. A lightly syncopated rhythm is supposed to be created, difficulty, this, hushed by an always present and regular accompaniment.
During the exercise no.21 all the five notes are exploited, both with the left and with the right hand, and, in my opinion, it has a rather relevant difficulty in the last measure of the first line, where left and right notes don’t play at the same moment. The rest of the exercise is rather obvious and regular.
It’s true, maybe I’ve been too much terse but there no relevant news, there’s only to play!
That’s a video with the execution: