Measures 1 to 27

Exposition, bars 27 to 43

• The subject (S in red) introduces the motifs a-e, which will be developed in the fugue.
• The real answer (A in blue) is in D minor, the dominant key, and it features rhythmic and melodic variations. Each appearance of the subject in this fugue will be varied. See below for a discussion of these variations.

Here we detail all the subject variants through the fugue:

We start with an answer that is already varied:

• The notes in orange indicate the variants.
• Notes that have been added are indicated with a '+'.
• The octave higher is indicated with the symbol 8^va.

Measure 48:

• Bach discards the first two notes of the subject.
• The subject is divided into two voices.
• He adds some notes and lowers others by an octave (8ba).

Measure 56:

• Bach discards the first notes again.
• We find added notes and octave changes.

Measure 71:

• The first notes reappear.

Measure 79:

• The first notes disappear.
• The subject is divided into two voices.
• Added notes and octave changes.
• Highly varied finale.

Measure 102:

Measure 130:

Measure 150:

• Bach doubles the first notes at the sixth.
• The subject is divided into two voices.
• Octave changes and numerous variations.

Measure 176:

• Final presentation of the subject.
• Bach doubles the first notes again, this time to the tenth (third plus an octave).

 

Measures 43 to 55

• Measures 43 to 47: a first episode based on motifs e and c_i (inverted c).
• Measures 48 to 54: the fragmented subject reappears in two voices: The first voice uses motif a, and the second voice uses motif b. Starting in measure 50, the second voice continues as an accompanying bass.
• Measure 54: a third voice appears, and we resolve to G minor with a perfect authentic cadence.

Measures 55 to 79

• Measures 55 to 59: we immediately modulate to D minor and a varied answer appears in measure 56. Second exposition or 4-voice fugue? We lean toward a second exposition.
• Measures 63 to 71: Bach insists on motif c (inverted in measure 68) in a march that leads us to B-flat major.
• Measures 71 to 79: subject in Bb major.

Measures 79 to 109

• Measures 79 to 88: an episode uses motifs b and a and brings us back to G minor.
• Measures 88 to 95: a new fragmented and varied subject begins in G minor and ends by modulating to B-flat major.
• Measures 96 to 102: an ascending progression starting at the end of the subject leads us to F major.
• Measures 102 to 109: a fragmented and varied subject begins in F major and ends in D minor..

Measures 109 to 137

• Measures 109 to 128: the episode opens in D minor, ascending fourths modulate to G minor, and it concludes in C minor.
• Measures 130 to 137: the key of C minor is affirmed by the varied subject.

Measures 137 to 157

• Measures 137 to 150: we start in B-flat major to reach G minor.
• Measures 150 to 157: subject in G minor. Its first notes appear doubled at the sixth.

Measures 157 to 183

• Measures 157 to 165: we begin in G minor, then return to B-flat major.
• Measures 166 to 170: we return to G minor. This is the climactic point of the prelude.
• Measures 171 to 175: G minor dominant pedal.
• Measures 176 to 183: subject with its first notes doubled at the tenth.

Measures 183 to the end

• Measures 183 to 196: high harmonic tension section, we remain in G minor, but Bach emphasizes the subdominant and dominant degrees through secondary chords.
• Measures 197 to 208: motives a and b lead us to a dominant pedal of the IV degree.
• Measures 208 to 214: pedal of the dominant of the IV degree.
• Measures 214 to the end: an ascending movement with secondary subdominant and dominant chords leads us to the final bars.

Complete Prelude