The prelude is 35 bars long and consists mostly of broken chords. Below are the first four bars of the prelude:
The prelude continues like this with different variations on harmony and change of key. The prelude ends with a single C major chord.
Fugue
The fugue is 27 bars long and is written for four voices. It starts with a two-measure subject in the alto voice. The first voice to join is the soprano, which replies with the answer in the dominant key.
The answer is repeated in the tenor and bass voices, respectively, when they enter. The piece then modulates through various related keys, with the subject being repeated in each of the four voices. The piece eventually ends up back in the home key. It ends with each voice stopping at a note and holding it until the end, forming a C-major chord.
Legacy
Schwencke Measure
Some earlier editions of the prelude contain an extra bar between bars 22 and 23 known as the "Schwencke measure", a measure allegedly added by in an attempt to correct what he or someone else erroneously deemed a "faulty" progression, even though this sort of progression was standard in the music of Bach's time.
However, according to Hermann Keller, "Schwencke was a sophisticated and well-informed musician who was probably not thinking of improving Bach." Measure 22 contains an F in the bass, which skips to A in measure 23, creating a diminished third; while the Schwencke measure has a G in the bass of a minor chord with C as its rootborrowed from the parallelharmonic minor. The A may be considered as its enharmonic, G, which creates a major second step with F, but A functions as an upper leading-tone. Franz Kroll may have been the first to question and edit the measure, first in 1862, and the measure does not occur in Bach's student Heinrich Gerber's 1725 manuscript copy. August Halm was also critical of the measure, questioning its logic as early as 1905.
Gounod's "Ave Maria"
composed a melody that was designed to be based on the prelude; a setting of that melody to Ave Maria is popular. The edition of the prelude used by Gounod contains the Schwencke measure.
20th Century
compared this Prelude to the introductory bars of Bach's famous Prelude of Cello Suite No. 1, in a video named Rostropovich interprets Bach, filmed in 1991 at the Basilique Sainte Madeleine in Vézelay, France. "Repent Walpurgis", the last track on the debut album by progressive rock group Procol Harum contains an arrangement of the prelude by band leaderGary Brooker.
