Bach: Prelude and Fugue No.18 in G♯ minor, BWV 887 Analysis

Analysis

Prelude

Bach Prelude and Fugue No.18 in G# minor BWV 887 Analysis 1

SUMMARY:

This Period is constructed upon the figures seen in the above bars.

Bars 1-24: Period I. Ending with a Perfect Cadence in Dominant Major, D sharp; double bar.

Bars 25-50: Period II. Starting with a reproduction of the Opening material in the key of the Dominant major, and ending with a Perfect Cadence in the Tonic minor, G sharp.

REMARKS:

Two Themes are used in this Prelude. Theme I (Bars 1,2) is divisible into two contrasted parts, of one bar each. Theme II (which makes its first appearance at Bar 8 in the upper part), has also two divisions, (1) at Bar 9, (2) at Bar 10.

At Bar 4, the position of the two upper parts contained in Bar 2 are Inverted, the Bass remaining the same for both.

At Bars 5-8 a new detached figure appears in the upper parts, and is worked in a descending Sequence.

At Bars 8-11 Theme II appears in the upper part, the Bass meantime having a figure, the first five notes of which are derived from Theme I. Both parts work Sequentially descending.

At the Start of Period II the Opening Theme is transplanted into the key of the Dominant Major (D sharp). Sequential work following up to Bar 29, when on the second beat of this bar the upper figure is slightly altered, thus allowing Bar 30 also to be in Sequence with it.

Bars 36-39 are a transposition a fifth higher of Bars 8-11 in Double Counterpoint.

Both Periods are capable of subdivision.

  1. Period I divides at Bar 8, where there is  Perfect Cadence to the Dominant Minor (D sharp), and at Bar 15 where there is a Perfect Cadence to the Supertonic Major (A sharp, Dominant of the Dominant).
  2. Period II divides at Bar 40, where there is a Half Cadence on the Dominant previous to the resumption of the original Theme in Bar 41.

The concluding bars of Period II (Bars 47-50) should be compared with the concluding bars of Period I (Bars 21-24).

This Period is built mainly upon the early Binary framework, but there are many indications of an endeavour to stretch beyond it into the more extended form as seen in the Modern Sonata. The first part ends in the Major key of the Dominant, and the second part begins by quoting the Opening Theme shifted into the new key, with a characteristic figure now assigned to the Bass; but, what is notable is that a free reign is given to modulation, making the whole section prophetic of the more ample “Development Section,” as it appears in the Modern Sonata. The Opening Subject is recapitulated (Bar 41) with slight modification in the interest of variety, and the concluding bars, by a judicious curve, reproduce in the Tonic key by the corresponding bars which appear in the Dominant in the first part. (Compare Preludes 12 and 15, Book 2).

 

Fugue

Bach Prelude and Fugue No.18 in G# minor BWV 887 Analysis 2

ANALYSIS:

ENUNCIATION SECTION:

Bars 1-5: Subject in Treble [G sharp minor].
Bars 5-9: Real Answer in Alto, with Counter-subject in Treble [D sharp minor].
Bars 9-13: Codetta, modulating from D sharp minor, through B major, to G sharp minor.
Bars 13-17: Subject in Bass. Counter-subject absent [G sharp minor].
Bars 17-19: Codetta, modulating from B major to G sharp minor.
Bars 19-23: Subject in Alto, with Counter-subject in Bass [G sharp minor].
Bars 23-33: Episode I, modulating from G sharp minor to D sharp minor.
Bars 33-37: Answer in Bass. Counter-subject absent [D sharp minor].
Bars 37-45: Episode II, modulating through B major to D sharp minor.
Bars 45-49: Answer in Treble. Counter-subject absent [D sharp minor].
Bars 49-55: Episode III, modulating from D sharp minor to G sharp minor.
Bars 55-59: Subject in Bass. Counter-subject (slightly altered) in Alto.
Bars 59-61: Codetta, modulating from G sharp minor to D sharp major.
Bars 61-65: Theme absent. Counter-subject in Treble [D sharp minor].
Bars 65-66: Codetta, modulating from D sharp major to G sharp minor.
Bars 66-70: Theme absent. Counter-subject in Alto [G sharp minor].

MODULATORY SECTION:

Bars 71-75: Theme absent. Counter-subject in Bass [C sharp minor].
Bars 75-79: Codetta, modulating from C sharp minor to G sharp minor.
Bars 79-83: Theme absent. Counter-subject in Treble [G sharp minor].
Bars 83-97: Episode IV, modulating from G sharp minor, through D sharp minor, and back to G sharp minor.
Bars 97-101: Subject in Bass, with Counter-subject in Alto [G sharp minor].
Bars 101-103: Codetta, modulating from G sharp minor to D sharp minor.
Bars 103-107: Answer in Treble, with Counter-subject in Alto [D sharp minor].
Bars 107-111: Codetta, modulating from D sharp minor, through G sharp minor, to C sharp minor.
Bars 111-115: Subject in Alto, with Counter-subject in Treble [E major].
Bars 115-125: Episode V, modulating from E major to G sharp minor.

RECAPITULATORY SECTION:

Bars 125-129: Subject in Alto, with Counter-subject in Bass [G sharp minor].
Bars 129-135: Episode VI, modulating from G sharp minor, through D sharp, and back to G sharp minor.
Bars 135-139: Subject in Treble, with Counter-subject in Alto [G sharp minor].
Bars 139-143: Coda.

SUMMARY:

Exposition: Bars 1-17.
Counter-exposition: Bars 33-59.
Codettas: Seven.
Stretti: None.
Episodes: Six.
Dominant Pedal: Bars 93-95.
Coda: Bar 139-143.

REMARKS:

  1. This Fugue has a “real” Answer, and would be called a “real” Fugue.
  2. The treatment of the Counter-subject is exceptional. At Bars 13, 33, and 45 it is altogether absent, its place being occupied by a part written in ordinary counterpoint. At Bars 66, 71, and 79 it appears by itself, the subject at these points being absent.
  3. At Bar 19 the Subject in the Alto is called “a redundant entry,” being contrived to show the Counter-subject in a different position as regards the Subject from that which it occupied in the Exposition. Here it is below the Subject; in the Exposition it was above it (see Bars 5 and onwards).
  4. The keys of the Tonic and Dominant reign supreme for 70 bars (roughly speaking, through half of the entire Fugue), when the Counter-subject is brought in by itself in the key of the Subdominant minor, C sharp.
  5. The Codettas are numerous and of great importance (see Analysis).
  6. The Episodes are of simple construction. They are built upon reminiscences of the Subject and Codettas.