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
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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 (G major).
The answer is repeated in the tenor and bass voices when they enter. The soprano then repeats the subject, to which the tenor answers in the dominant, modulating to G minor and then to G. The piece then continues with each of the four voices restating the subject multiple times throughout, modulating to various related keys. A four-voice canon is formed in bars 14 - 15. The fugue then culminates with a four-bar long forming of the tonic triad.
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 Christian Friedrich Gottlieb Schwencke in an attempt to correct what he or someone else erroneously deemed a "faulty" progression (though it may be accidentally corrupted manuscript(s) associated with Schwencke), even though this sort of progression was standard in the music of Bach's time.[1]
However, according to Hermann Keller, "Schwencke was a sophisticated and well-informed musician who was probably not thinking of improving Bach."[2]
Charles Gounod composed a melody that was designed to be based on the prelude; it was later used as a setting to Ave Maria. The edition of the prelude used by Gounod contains the Schwencke measure.[1]
20th century
Arvo Pärt's "Credo" is built around Bach's C major prelude, first unravelling it through the central cacophonous twelve-tone part of the work, then remerging on the piano with the chorus and orchestra joining in harmony for the massive finale.
Mstislav Rostropovich compared this Prelude to the introductory bars of the prelude of Bach's Cello Suite No. 1, in a video named Rostropovich interprets Bach, filmed in 1991 at the Basilique Sainte Madeleine in Vézelay, France.
^ abcBarber, Elinore (1970). "Questions to the editor". Bach. 1 (1): 19–22. JSTOR41639775. The insertion of the measure shows a fundamental misunderstanding of Bach's skip in the bass from F-sharp to A-flat. It seems unlikely that any knowledgeable contemporary of Bach's would have tried to 'correct' this not uncommon bass progression.
^Rothfarb, Lee Allen (2009). August Halm: A Critical and Creative Life in Music. University of Rochester Press. p. 56. ISBN9781580463294.
^Lockwood, Lewis; Webster, James; Reynolds, Christopher; eds. (1996). Beethoven Forum, p. 70. University of Nebraska. ISBN9780803229211. Halm (1905). "Musikalische Logik", Der Kunstwart 18, pp. 486-487.