The prelude is 70 bars long, and is written in binary form, of which the first half is 28 bars long and ends in A-flat major. The second half modulates through a variety of keys before returning to the home key of F minor. Below is the opening sentence of the prelude:
The first four measures of this sentence have two voices leading the melody in thirds, and another voice leading the bass line. After four measures, only two voices continue. One voice plays the root of a chord, while the second voice plays a broken chord around it. This continues like so for another four measures, and ends with an
perfect cadence. Together, these two sentences create a compound period
, and the first part of a small binary.
Following the compound period, the second part of the small binary starts. It consists of one voice playing broken chords and two other voices leading a melody, and is eight measures long. A perfect cadence in A♭ major concludes the small binary, and thus ending the theme of the prelude.
The prelude ends with a two-measure
codetta
, which consists of a perfect cadence in the home key.
Fugue
The fugue is 85 bars long, and is written for 3 voices. Below is the 4-measure subject of the fugue: