Prelude and Fugue in C major, BWV 846

The Prelude and Fugue in C major, BWV 846, is a keyboard composition written by Johann Sebastian Bach. It is the first prelude and fugue in the first book of "The Well-Tempered Clavier", a series of 48 preludes and fugues by the composer. An early version of the prelude, BWV 846A, is found in the "Klavierbüchlein für Wilhelm Friedemann Bach".
Analysis.
Prelude.
The prelude is 35 bars long and consists mostly of broken chords. Below are the first four bars of the prelude:
 «
 \new PianoStaff «
 \new Staff «
 \clef treble \key c \major \time 4/4
 \new Voice \relative c" {
 \voiceOne r8 g16 c e g, c e r8 g,16 c e g, c e 
 r8 a,16 d f a, d f r8 a,16 d f a, d f
 r8 g,16 d' f g, d' f r8 g,16 d' f g, d' f
 r8 g,16 c e g, c e r8 g,16 c e g, c e 
 \new Voice \relative c' {
 \voiceTwo r16 e8._~ e4 r16 e8._~ e4
 r16 d8._~ d4 r16 d8._~ d4
 r16 d8._~ d4 r16 d8._~ d4
 r16 e8._~ e4 r16 e8._~ e4
 »
 \new Staff «
 \clef bass \key c \major \time 4/4
 \new Voice \relative c' {
 c2 c c c b b c c
 » »
</score>
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 (G major).
\relative{
\new Staff \clef treble \key c \major \tempo 4=70 \set Score.tempoHideNote = ##t
 \override Score.BarNumber #'transparent = ##t
 \new Voice= "Alto"
</score>
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 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.
 «
 \new PianoStaff «
 \new Staff «
 \tempo 8=116 \set Score.tempoHideNote = ##t
 \clef treble \key c \major \time 4/4
 \new Voice \relative c' {
 r8 b16 c es b c es r8 b16 c es b c es
 »
 \new Staff «
 \clef bass \key c \major \time 4/4
 \new Voice \relative c {
 \voiceOne r16 es8._~ es4 r16 es8._~ es4
 \new Voice \relative c {
 \voiceTwo g2 g
 » »
</score>
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 (second inversion) minor chord with C as its root borrowed from the parallel harmonic 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 (parallel natural or descending melodic minor). 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. was also critical of the measure, questioning its logic as early as 1905.
Gounod's "Ave Maria".
Charles Gounod 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.
Mstislav Rostropovich 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 leader Gary Brooker.
External links.
Interactive media
Sheet Music