A weighty, perpetual motion étude reminiscent of a sudden, violent storm that arrives and departs abruptly. While the upper voice passages in 16th notes race across the keyboard unrestrainedly, the left hand, centered on octaves, also covers a wide range, mixing lightness and gravitas, appearing sometimes as accompaniment, sometimes as melody, and surging forward. It goes without saying that performing it fully requires both virtuosity and musical interpretation. Furthermore, the highly effective outer sections, characterized by wide-ranging cadenzas, were not present when the piece was initially completed but were added before publication.