Noctave
The piece
The last of the eight impromptus, in F minor, is marked Allegro scherzando and written in 3/8. It plays with off-beats and shifted accents, flashing scales and trills; a more lyrical middle part runs through it before the opening returns. It ends with a Più presto and a descending scale played by both hands over several octaves.
The difficulty lies in speed and lightness: 120 to the quarter here, about 80 bars a minute. The scales must stay even from end to end; practise them in groups, slowly, keeping the same fingering every time. Respect the off-beat accents without hardening the sound, and the rests, which count as much as the notes. Save some energy for the end: the Più presto speeds up again, right to the last scale.