The G-minor Presto
The Presto’s continuous fast notes and two pairs of repeat signs recall nineteenth-century perpetual motions and binary forms. Indeed, Johannes Brahms (1833–97) turned this very movement into two compositions with precisely those features: piano etudes for developing facility.1 In one etude he kept Bach’s solo in the right hand and wrote continuous sixteenths against it in the left hand, and in the other he kept Bach’s solo in the left hand and wrote continuous sixteenths against it in the right hand.
But similarities between this movement and later perpetual motions and binary forms are deceptive. The dynamic of Bach’s rhythms and forms is fundamentally at odds with later apparently similar compositions. This chapter contrasts Bach’s Presto (and some other continuous-rhythm movements from the solo-violin works) with nineteenth-century perpetual motions and contrasts the Presto’s two-section outline with later binary forms. Differentiating Bach’s practices from those of later eras allows his own inherent structures to emerge.
The Moto perpetuo by Niccolò Paganini (1782–1840), whose opening appears in Example 5-1a, is the nineteenth-century epitome of its genre. The melodic fluidity encourages violinists (and even flutists—witness James Galway’s famous recording) to aim for a thrilling sense of speed. This fluidity is not merely a factor of the actual speed—it arises even more from the rhythms inherent in the melodic line. In the first four beats of the melody, for instance, a chord tone appears on every strong, odd-numbered sixteenth (the first and third sixteenths of each beat) and a nonharmonic tone on almost every weak, even-numbered sixteenth. Every nonhar-