Noctave
The piece
A pupil of Beethoven and later the teacher of Liszt, Czerny left more than eight hundred opus numbers, many of them for teaching. Op. 821 gathers one hundred and sixty exercises, each eight bars long and each devoted to a single motion. This one isolates the repeated octave: the right hand strikes every octave two or four times in sixteenth notes while the left hand lays down a slurred two-voice accompaniment. The tune is simply the top of those octaves, moving mostly by step.
The figures speak for themselves: 121 octaves in the right hand, 83 repeated notes, close to six attacks per second. What tires you out is hitting from the whole arm. Set the hand shape once, thumb and fifth finger spread to the octave, and let the wrist bounce loosely without lifting the fingers. Listen above all to the last stroke before each change of note, which tends to get crushed. In the left hand, honour the slurs and hold the half notes, a calm foil to the restless right. If your forearm stiffens before bar eight, lower the tempo rather than push through.