the 'Wohltemperirtes Clavier' is an instance. The exposition, which occupies the first four bars, is for three voices only, and the fourth voice does not enter till the 19th bar, when it brings in the subject by augmentation, and the last ten bars of the fugue are for four voices. A similar example will be seen in Bach's Organ Fugue in C major—
of which the first 48 bars are a four-part fugue, without pedals. At the 49th bar the pedals enter with the subject in augmentation (as in the case last mentioned), and from this point to the end the fugue is in five parts.
204. We now give an exposition of a four-part fugue, taking the same subject as before, but adding an entirely different countersubject and beginning with a middle voice. We choose the alto, so as to retain the same key.
![\new ChoirStaff << \override Score.BarNumber #'break-visibility = #'#(#f #f #f)
\new Staff \relative a' { \key d \major \time 4/4 \numericTimeSignature
R1*6 \[ a4^"A" d cis r8 fis16 e | d8 cis b4 a8 \] s }
\new Staff \relative d' { \clef alto \key d \major \numericTimeSignature
\[ d4^"S" g fis r8 b16 a |
g8 fis e4 d8[ \] fis^\markup \tiny \italic "Codetta." e d] |
\[ cis8^"CS" d16 e fis8 gis a e a4 ~ |
a ~ a16 gis fis gis a8[ \] d,16 e] fis8 e |
d d' cis b a4. g16 a | b8 a g a16 g fis8 d16 e fis e fis gis |
a gis fis e d8 e ~ e fis16 g a8 fis ~ |
fis16 gis a8 e b' e,16 fis e d_"&c." }
\new Staff \relative a { \clef tenor \key d \major \numericTimeSignature
R1*2 \[ a4^"A" d cis r8 fis16 e |
d8 cis b4 a8[ \] b a g! |
\[ fis^"CS" g16 a b8 cis d a d4 ~ |
d ~ d16 cis b cis d8[ \] a gis b] |
e, fis16 gis a8 b cis d16 e fis e d cis |
b8 cis16 d e fis d e cis d cis b }
\new Staff \relative d { \clef bass \key d \major \numericTimeSignature
R1*4 \[ d4^"S" g fis r8 b16 a | g8 fis e4 d8[ \] fis e d] |
\[ cis^"CS" d16 e fis8 gis a e a4 ~ | a ~ a16 gis fis gis a8 \] s } >>](http://upload.wikimedia.org/score/e/p/epyfk9nr6qhsqqb47evijxwx3qgq7tf/epyfk9nr.png)
