This is an Allegro in three-voice fugal form. The theme (subject) spans from the first beat of bar 1 to C-sharp on the third beat of bar 2. As is typical, it modulates to many keys, and the theme should be performed each time with an atmosphere, volume, and tone quality appropriate to the respective key and register.

Up to this point, it is no different from a standard fugue. However, in the case of this Allegro, the independence of the voices is exceptionally challenging, and this constitutes a primary difficulty.

For instance, observe the movement of the soprano and alto from the second beat of bar 8 to the fourth beat of bar 9. When written in this manner, the note following the soprano E on the second beat should ideally be D-sharp on the fourth beat. However, due to the alto F-sharp on the third beat, the listener perceives E, F-sharp, D-sharp, E, C-sharp, D-sharp, B-sharp, C-sharp. Beyond this, such figures tend to segment the music vertically, thereby impeding its horizontal flow.

Such figures are frequently encountered in this Allegro. In these instances, a viable approach is to play the soprano distinctly while rendering the alto with a subdued tone quality and volume. This prevents interference with the sustained soprano line. To put it differently, successful execution is achieved by continuously listening to the sustained soprano notes (those extended by ties) with one's own ear during performance.