Bach: Prelude and Fugue No.4 in C♯ minor, BWV 873 Analysis

Analysis

Prelude

Bach Prelude and Fugue No.4 in C# minor BWV 873 Analysis 1

SUMMARY:

Bars 1-17: Period I. Theme I (Bars 1-5). Establishes the Tonic, C sharp minor and works to its Dominant Major (G sharp) (Bar 5) before returning to the original key (Bar 7). Theme I undergoes a varied treatment (Bars 7-11). Ending with Perfect Cadence in the key of the Dominant Minor, G sharp.

Bars 17-27: Period II. Beginning in G sharp minor, it touches C sharp major and B major before ending with Perfect Cadence in the key of the Relative Major, E.

Bars 27-33: Period III. Starting with new material, it moves by Imitative work through the Subdominant minor (F sharp) (Bar 29), then through B minor (Bar 31), ending with Perfect Cadence in the key of the Subdominant Minor, F sharp.

Bars 33-39: Period IV. Ending with Perfect Cadence in the key of the Tonic Minor, C sharp.

Bars 39-62: Period V. Ending with Perfect Cadence in the key of the Tonic Minor.

REMARKS:

The figures in each of the three parts are contrasted with each other.

At Bar 7-11, the Alto strictly imitates the Treble (Bar 1-5) in the Octave below.

At Bars 27 a figure (Theme II) founded on the Bass of Bars 1 and 2 is brought into prominence by the Treble in the Relative Major, imitated by the Alto in Bar 28, and by the Bass in Bar 29. This constitutes a new exposition of an idea when the piece arrives at the Relative Major.

At Bars 33-37 Theme I appears in full in the Alto in the key of the Subdominant Minor, the Bass being also a strict transposition into this key of Bars 1-5.

Period V (Bar 39) starts with Theme I, in the Treble in the original key as at the commencement, but with more vivacious surroundings.

At Bars 43-47 occurs a figure in the Bass (derived from Bar 2 and 3) which is used in a descending Sequence, accompanied by the two upper parts in florid counterpoint.

At Bar 50 Theme II appears with a prefix of three semiquavers (sixteenth notes), answered in Bar 51 by the Alto, and in Bar 52 by a free version in the Bass.

Period I is capable of subdivision at Bar 5, where it rests for the moment upon the Dominant as a centre.

Period V also divides at Bar 43 for the same reason.

The other Periods are not capable of subdivision.

 

Fugue

Bach Prelude and Fugue No.4 in C# minor BWV 873 Analysis 2

ANALYSIS:

ENUNCIATION SECTION:

Bars 1-2: Subject in Bass [C sharp minor].
Bars 2-3: Real Answer in Treble. No Counter-subject [G sharp minor].
Bars 4-5: Codetta from G sharp minor to C sharp minor.
Bars 5-6: Subject in Alto [C sharp minor].
Bars 6-16: Episode I, modulating through E major back to C sharp minor.
Bars 16-17: Subject in Treble [C sharp minor].
Bars 17-19: Answer in Alto [G sharp minor].

MODULATORY SECTION:

Bars 20-21: Subject in Bass [E major].
Bars 22-23: Codetta from E to B major.
Bars 24-25: Subject in Treble by Inversion [B major].
Bars 26-27: Answer in Alto by Inversion [C sharp minor].
Bars 28-29: Subject in Bass by Inversion [C sharp minor].
Bars 29-30: Codetta from C sharp minor to F sharp major.
Bars 30-31: Subject in Alto [C sharp minor].
Bars 31-48: Episode II, modulating from C sharp minor, through G sharp minor, F sharp minor, B major, F sharp minor, and back to C sharp minor.
Bars 48-49: Subject in Treble [C sharp minor].
Bars 49-53: Episode III, modulating from C sharp minor to A major.
Bars 53-56: Subject in Alto by Inversion (slightly altered as to skips) [A major].
Bars 55-56: Subject in Bass [C sharp minor].
Bars 56-61: Episode IV, touching G sharp minor and back to C sharp.
Bars 61-62: Answer in Alto.
Bars 62-66: Episode V, modulating from C sharp to E major and back to C sharp.

RECAPITULATORY SECTION:

Bars 66-67: Subject in Alto [C sharp minor].
Bars 67-69: Answer in Bass (slightly altered in several places) [G sharp major].
Bars 69-71: Coda.

SUMMARY:

Exposition: Bars 1-6.
Counter-exposition: (Incomplete) Bars 16-19.
Counter-subject: None.
Codettas: Three.
Stretti: None.
Episodes: Five.
(1) Dominant Pedal: Bars 59-60.
(2) Dominant Pedal: Bars 66-67.
Coda: Bars 69-71.

REMARKS:

  1. This Fugue has a “real” Answer, and would consequently be called a “real” Fugue.
  2. The Subject and Answer are used by Inversion in the course of the Fugue, the earliest example being in the Treble of Bar 24. Free Inversion is employed – i.e., the position of the tones and semitones is note strictly followed in the inverted form.
  3. The ground covered by the five Episodes – not to mention the Codettas – is rather more than half of the entire Fugue.
    1. Episode I (Bar 6) which stands between the Exposition and the Counter-exposition, is formed upon fragments of the latter part of the Subject, which are pretty equally distributed between the three parts.
    2. Episode II (Bar 31), up to Bar 35, is formed upon the same material as Episode I. At this bar a new Theme appears in the Treble, the two under-parts containing fragments of the Subject.
    3. Episode III and IV (Bars 49 and 56) are built upon the same material as Episode I.
    4. Episode V (Bar 62) has in its early part a detached figure derived from the Subject in the Bass, the two upper parts being formed upon reminiscence of the Subject.