WTC I/22 in Bb minor -- Prelude

    from Siglind Bruhn
J.S. Bach's Well-Tempered Clavier
In-depth Analysis and Interpretation

I/22.1.1 The prelude-type

This prelude appears determined by its gently swinging pulse which is conveyed by an overwhelmingly uniform rhythmic pattern. The entire piece builds upon only two rhythmic models which can, since the second is a very close variation of the first, even be regarded as two versions of only one archetype. They are:

(ex. 37a: Rh1) (ex. 37b: Rh2)

(The only two exceptions, with six consecutive sixteenth-notes, occur in cadential context, in bars 194 and 234).

The effect of this rhythmic uniformity is a meditative atmosphere within which transitory emotional upheavals seem of subordinate importance.


I/22.1.2 The overall design of the prelude

The first cadence concludes on the downbeat of bar 3. Until then, however, the harmonic progression develops over a tonic pedal, thus giving the impression that "the piece has not quite begun". Moreover, the cadence supports the melodic motive presented in the upper voice. This harmonic close should therefore be interpreted as marking the end of a simple phrase rather than that of a structural section. The second harmonic progression concludes, still in the tonic key, on the middle beat of bar 7. Both the way in which this cadence is prepared and that in which the subsequent development begins designate this closure as a structurally relevant caesura.

There are altogether four structural sections in this prelude, two of which contain harmonic subdivisions of subordinate structural importance.

I bars 1- 7 beat 3 tonic
  (bars 1-3d, 3-7m)  
II bars 7-13 beat 2 tonic to dominant
III bars 13-20 beat 1 dominant - dominant relative - dominant
  (bars 13-15d, 15-20d ending in imperfect cadence)
IV bars 20-24 dominant to tonic

As for analogies within this structural pattern, there is only one but it is most obvious as it pretends a "recapitulation": bars 20/21 take up bars 1/2, transposed to the dominant key and with slight variation in the middle voices.


I/22.1.3 Practical considerations for performers

The basic character of the prelude as determined by the above-mentioned rhythmic uniformity, is rather calm. This is supported by the pitch pattern which consists to a very large extent of second intervals. Another striking feature that influences the character appears in the frequent pedal notes;

see bars 1-3d: Bb
  6-7d: F
  7: Bb
  9m-10d/11-12d: Bb
  20-22d: F
  23/24: Bb


The tempo in which this character can best be expressed is fairly slow. The quarter-notes of the time signature can be imagined as depicting a very solemnly swaying movement; the eighth-notes which are perceived as the continuous pulse should be completely without haste. The articulation required in such a piece is a very dense legato. (As this prelude contains such a large number of repeated notes, the help of the damper pedal will probably be unavoidable to produce the desired smooth result. This, however, needs careful pondering. Using the pedal only where there are repeated notes would create an uneven tone color. Thus regular and painstakingly equal pedaling throughout the piece is the only alternative to not using the pedal at all. The "cleanest" solution would be to depress the pedal always after the last sixteenth-note of each eighth-note beat, and to release it immediately with the beginning of the following eighth-note. The nature of this meditative piece, however, admits also a slightly less transparent execution in which the pedal is simply changed on each eighth-note, thus giving the second sixteenth-note in each rhythmic figure a somewhat murky coloring. Eighth-notes, however, must be very clear.)

The score does not contain any ornaments.


I/22.1.4 What is happening in this prelude?

The pulse in this metrically determined prelude, as was already mentioned, is two-fold: the main swinging motion is in quarter-notes, whereas the consistent pounding is experienced in the eighth-notes. This effect of ambivalence is established in the very first bar where the unremittingly throbbing pedal note contrasts not only with the rhythmic motive but also with the mid-texture chords - and these, in their upbeat/downbeat pattern, underpin the larger quarter-note pulse. In ex. 38, the three levels of this texture are written in separated staves.

While the initial phrase of the prelude, as can be observed in this example, displays a constantly changing number of voices (from four to seven, though mostly five), the texture from bar 3 up to the downbeat of bar 20 is in consistent four-part writing. The "recapitulation" of the initial phrase then resumes the five-part texture, with extra voice-splitting only in bar 22 (beat 2: seven voices; beat 3: nine voices).

rhythmic model:


chordal background:


repeated pedal:


While the initial phrase might easily pass for the introductory line of a homophonic composition, there are several portions in the prelude which must be described as - modestly yet very consistently - contrapuntal. Quite a plausible interpretation of these confusing data is the following: the prelude can be regarded as a piece in four-part writing, with an additional "bass 2" in the initial phrase and its recapitulation, as well as a few irregular voice-splitting. (In bar 22, for instance, bass 2 would be assumed as splitting first to the third Eb/C, then to the triad Eb/C/A, only to resume its former F on the second beat of bar 23.) Such an interpretation contributes much to a better understanding both in listening and performing.

What remains to be done is a more detailed analysis of the development of melodic figures and changing textures.

The soprano motive establishes, supported by the alto in double thirds, the first rhythmic pattern (Rh1) in bars 1-3d. (It will here be referred to as M1). This is imitated, with a variation in its tail, by the bass (see bars 3-5d). Instead of being supported in double notes, the motive is accompanied here by a continuing figure in the highest voice which retains the first rhythmic pattern for one half bar and then proceeds to modify it to Rh2 (see bars 3-4d). The middle voices lengthen their earlier upbeat/downbeat pattern by an extra weak-beat chord.
From the second eighth-note of bar 4 onwards, alto and soprano commence a complementary pattern which soon (in bar 5) expands to pervade all four voices: on the one hand A+T (in double thirds, like the two melodic voices in bars 1/2), on the other hand S+B (joined only in rhythm but not in pitch outline, like the two melodic voices in bars 3/4). These two pairs alternate in such a way as to produce Rh2. In bars 6/7 one of the voices abandons the surface activity and retreats into a pedal (see S: bar 6, B: bar 7) while the others continue with Rh2 in free style.

The material introduced in this first section can be summed up as follows:

a melodic figure M1,
two rhythmic patterns Rh1, Rh2,
a homophonic texture with a weak/strong figure in the accompanying chords, later prolonged to weak/strong/weak,
a modestly polyphonic texture in complementary-rhythm pattern.

As will be seen right now, these are the building blocks from which the entire prelude is constructed.

The second section begins with M1, varied and extended (see S: bar 7m-10d). The bass, while obliging to the same rhythmic pattern, creates an independent pitch line, and the middle voices take up the lengthened weak/strong/weak pattern (similarly to bars 3/4). The harmonic development in this phrase pretends, with the bass descent from Bb to Bb, to remain in the tonic sphere; however, the final chord (see bar 10d) is actually an inverted V/V and represents an imperfect cadence in the key of the dominant. The second phrase of this section begins by combining the idea of the complementary pattern in double notes with a hint of imitation (see A/B: bars 10/11, imitated freely by S/T). This setting then gives way to a cadential close which appears as a free adaptation of the rhythmic pattern. (The final bar of this section also features a fifth voice - this time composed as "soprano 2" - which contributes a traditional do-si-do (keynote / leading-note / keynote) figure; see bars 12/13: F-E-F.)

The third section relies entirely on the complementary pattern in double notes. Its first phrase presents this pattern in simple imitation, without stretto overlapping (see S/B, A/T: bars 13-15), while the second phrase places it in the denser texture as introduced in bars 10/11, this time with soprano and bass as the two leading voices (see bars 15-17). The tail of this section, like those of the other sections freer in style, sets out with a joint four-part realization of Rh2 (in bar 18) and ends by combining features from the first and second sections (compare the sustained soprano and the descending bass in the first half of bar 19 with bar 6, and the bass repetitions leading into an imperfect cadence in bars 19/20 with bars 9/10).

In the fourth section, the varied recapitulation of the initial phrase accompanies the leading soprano motif with parallels first in the tenor, then in the alto (as in the initial phrase) and finally in both (see bar 21); it gives up Rh1 for Rh2 at the end of bar 21 and ends in a multiple-voiced fermata on a vii7 chord. The ensuing cadential formula once more alternates the two rhythmic patterns, returns to the tonic pedal (both in the sustained soprano and in the repeated bass 2) and to the double-third texture (A/T).

The dynamic rise and fall in such a meditative prelude is obviously much smoother than in other pieces; it develops as a secondary feature and should never lure the listener away from the all-pervading pulse.

A dynamic representation which is both natural and unobtrusive would follow the course of the ascents and descents of pitch - both those in the overall design and in sudden leaps - with very gentle increases and decreases. As a result, the first section of this prelude represents a gradual swell of tension (approximately from p to mp) until bar 5, followed by a short release, while the second section represents a gradual decline (approximately from p+ to p-, to give an impression how gentle these modifications of intensity are), followed by a mild rebuild of the original piano color in the cadential formula. The third section begins with very delicate touch in the sparse texture of its first phrase, but in its second phrase engenders the strongest and steepest build-up of tension in this piece. This leads to the first overall climax (preferably no stronger than mf) on the second beat of bar 16, from which the remainder of the section descends in very gradual diminuendo. The fourth section contains the second overall climax which, despite its compact chord, should sound introverted and intense rather than extraverted and loud. The prelude closes after a final diminuendo on a soft note, thus giving the impression that the ending returns to the level of the beginning.



WTC I/22 in Bb minor -- Fugue

I/22.2.1 The subject

The question where the subject of the Bb minor fugue ends permits two answers. The trunk of the subject, which contains all the relevant harmonic steps, closes on the downbeat of bar 3. The four quarter-notes which follow (until bar 4d) could be regarded as a simple extension if they were not used with such striking consistency throughout the fugue. It is therefore appropriate to speak of a shorter and a longer version of the phrase. Following a terminology used originally for distinguishing metric endings in Greek poetry, these different shapes of the same trunk are often referred to as "male" and "female". The "male" version appears condensed, concluding with the last essential step without any softening addition. The "female" ending adds, in poetry, an unaccented pulse after the final accent; in music, it extends the tonic reached in the perfect cadence with notes which passively remain in the same harmony.

This regular extension is conceived as a smooth continuation, both in rhythm and pitch pattern, of the second half of the main body: bars 2 and 3 of the subject contain exclusively quarter-notes in stepwise motion. This gentle curve appears in sharp contrast to the beginning of the subject where two half-notes followed by a downbeat rest create rhythmic tension. At the same time, the falling perfect fourth, in itself a very relaxed interval, is followed (across the rest) by a minor ninth; this interval, very rarely used for horizontal progressions in Bach's time, expresses an emotional gesture of the highest intensity.

The question which, in this subject, needs careful pondering, is whether or not this exceptional melodic jump is really meant to be perceived - and played - as an interval, i.e. whether these two consecutive notes are immediately related and belong to an uninterrupted structural unit. This leads to the question of phrase structure. Quite independently from the concept of male or female endings, the phrase structure of this subject can be interpreted in two ways.

In the first option, the rest, together with the unusually large distance between the two notes enveloping it, is regarded as an indication of structural interruption, comparable to a comma in verbal language. The subject then consists of two subphrases which differ considerably in all features: the first subphrase commences on a strong beat and contains only two long note values in a falling fourth; the second subphrase commences on a weak beat and contains exclusively shorter note values in a progression of seconds.
In the second option, the rest is interpreted as tension sustaining, as a soundless continuation of the melodic flow, and the interesting interval is thus fully exploited. This minor ninth, whose tension is enhanced by the fact that it spans across a suspended downbeat, then becomes the main melodic focus of the subject.

The harmonic background to the subject can be depicted as follows (ex. 39):

One modification of the harmonization in the subject deserves mentioning. In several cases, the male ending (i.e. the note which falls on the downbeat of the third subject bar) is raised by a semitone and harmonized not by the tonic but by a major chord with seventh on the tonic root. This chord is heard as a dominant-seventh and resolved correspondingly onto the subdominant. The melodic line supports this modulation by placing the entire female ending one note lower, thus leading to the root of the target harmony. This harmonization - and its fairly frequent occurrence within the fugue - provides additional proof that the extension of the subject, initially presented as harmonically redundant, is actually an intrinsic part of the whole: in these modulating statements, the male ending does not provide the harmonic resolution but needs the subsequent bar to convey a satisfactory sense of closure.

The climax in this subject falls undoubtedly on the Gb on the second beat of bar 2. Even if one disregarded, for the time being, the melodic power which the preceding interval might attribute to this note, the Gb combines many tension-enhancing features. Not only does it sound highest in pitch, it also represents harmonically the subdominant, i.e. the most active step of the cadence, and melodically the minor sixth of the Bb minor scale, i.e. one of the natural leading-notes.

While the climax is followed, in whatever interpretation of the rest before it, by a gradual diminuendo (with a fairly steep decrease until the male ending and a gentler further subsiding in the female ending), the shaping of the notes preceding the Gb depends entirely on the concept of the phrase structure.

Performers who assume two subphrases, would conceive the F in the middle of bar 1 as the conclusion of the first structural unit and thus play it relaxed and comparably soft; the ensuing Gb would then appear as a new beginning, with no immediate relationship in either melodic or dynamic flow to the first bar. In this interpretation, the subject would thus appear in two diminuendo lines: one, launched by the initial note, short and steep; the other, commencing on the more powerful second climax, in gently lessening intensity.

Performers who assume that the subject consists of an indivisible phrase, would take the initial descending fourth to fulfill quite a different task; as the anchor of the high-tension interval it would be regarded as geared forward and incorporating a much higher degree of intensity than the initial Bb. In this interpretation, the subject would thus consist of a powerful dynamic build-up, from Bb through F and through the rest to the high Gb, followed by the gradual release in the quarter-notes.



I/22.2.2 The statements of the subject

The fugue contains twenty-two statements of the subject, presented in five voices; "v1" and "v5" refer to "voice one" and "voice five" respectively, counted from top to bottom. Those entries which contain the above-mentioned variation of the female ending which effects a modulation are marked with an asterisk, while statements which close on the male ending appear with a minus ("-").


bars 1 - 4 v1 12. bars 48 - 50 v5-
2. bars 3 - 6 v2 13. bars 50 - 52 v1-
3. bars 10 - 13 v3 14. bars 50m- 52 v2-
4. bars 12 - 15 v4* 15. bars 53 - 56 v4
5. bars 15 - 18 v5* 16. bars 55 - 58 v2
6. bars 25 - 28 v1 17. bars 55 - 58 v3
7. bars 27 - 29 v2- 18. bars 67 - 70 v1
8. bars 29 - 32 v4* 19. bars 68 - 71 v2
9. bars 32 - 35 v5* 20. bars 68m- 71 v3
10. bars 37 - 40 v2* 21. bars 69 - 72 v4
11. bars 46 - 48 v3- 22. bars 69m- 72 v5


(ex. 40):

The subject appears both in stretto and in parallel. The stretto settings involve two essentially different cases of premature succession. On the one hand there are those where only the female ending of the statement in the lead overlaps with the subsequent beginning (see bars 3, 12, 27, 55); on the other hand there are those entries where the distance is as close as possible, i.e. the second subject note in one voice becomes the initial note in the ensuing statement (see once in bar 50, twice in bar 68 and twice in bar 69). In the light of these strettos, the parallel entry in bars 55-58 might appear as an even closer stretto.

Few modifications occur in the melodic shape of the subject. Those which do appear are linked, in one way or another, to the adaptation which the subject suffers in its tonal answer where the original falling fourth is stretched to a fifth, and the ensuing large interval spans a minor tenth (see e.g. bars 3-6). While this tonally determined lowering of the subject's second note remains without effects for the closing on the tonic, some cross-combinations of these intervals occur which, in fact, alter the harmonic background of the subject statement. In bars 25-28, e.g., the combination of initial falling fourth with ascending minor tenth places the subject tail one note up and causes a modulation from Db major to Eb major; conversely, in bars 53-56 the falling fifth is combined with the ascending minor ninth, thus wreaking a modulation from Bb to Eb. A last-minute tonal adjustment can also happen by way of a variation in the female ending (see in bars 12/13 the final Eb).


I/22.2.3 The counter-subject

The Bb minor fugue contains no counter-subject. This may partly be due to the unusual female ending which frequently serves as a contrapuntal accompaniment to the beginning of the second or later subject entry in a group.


I/22.2.4 The episodes

The fugue contains six subject-free passages.

E1 bars 6 - 9 E4 bars 40 - 46
E2 bars 18 - 24 E5 bars 58 - 67
E3 bars 35 - 36 E6 bars 72 - 75

Two of these episodes, E2 and E5, develop from the statement preceding them by sequencing the second and third bars from the subject (see v5: bars 18-20, and, in a more modified version, v2/v3: bars 58-60).

E1 and E4 contain a motive, consisting of an inverted-mordent figure ascending to a dotted half-note on the downbeat. M1 is sequenced and imitated and can thus be called a genuine episode motive; it not only fills the entire subject-free passage but even extends slightly into the beginning of the next subject statement (see v1/v2: bars 11; v5/v2: bars 42-47; note that v2 is the uppermost of the three voices involved in these bars).

The two remaining episodes, E3 and E6, are essentially nothing but extended cadential closes. E3 features a short cadential-bass pattern (see bars 36/37) and a longer do-si-do (keynote / leading-note / keynote) formula in v1 (bars 35-37), while in E6 these figures are of opposite length (see v5 in whole-notes: bars 73-75, v1 in half-notes bars 74/75).

In addition, the same combination of cadential traits can also be found at the end of E2 (see bars 23-25). The structurally analogous E5 does not contain this cadential close; instead it appears there (easily overlooked) in the context of a full-fledged subject statement, in bars 53-55.

As these details reveal, the episodes in this fugue are arranged in a symmetrical pattern of structural correspondence: E1 relating to E4, E2 to E5, and E3 to E6. With regard to the dynamic outline in each, E1 and E4 with their ascending sequences of M1 clearly describe an increase in tension and thus lead from the preceding subject statement onwards into the subsequent one. E3 and E6, on the other hand, clearly terminate a structural section. In the two intermediate episodes it seems worthwhile to observe the overall pitch tendency which is, in both cases, very pronounced. In E2, the initial sequence from the subject tail begins lower - and therefore probably softer - than the end of the preceding entry; at the same time, the first voice completes a descending line which had begun immediately after the disappearance of M1 and continued through two entire entries, in ever larger note values (see v1, bars 11-20: C-Bb-Ab-Gb-F-Eb, Db-C-Bb, Ab). This long descent is countered by sudden ascents in all five voices (see particularly bars 20, 21) which discontinue their build-up only towards the cadential formula at the closure of the episode. In the structurally corresponding E5, these lines seem reversed. The initial sequences from the subject tail begin from an elevated position (see bars 58/59) but are then followed by descending lines. The most prominent of these is the one in the uppermost voice which, as in E2, concludes in whole-notes (see v1 bars 62-67: Gb-F-Eb-Db-C-Bb-Ab-Gb-F). This episode thus creates its climax at the beginning and subsequently conveys an almost complete release, so extended that the anticipation for the events to come is heightened all the more.


I/22.2.5 Character, tempo, articulation, ornament realization

The basic character of this fugue must be described as rather calm, not only because of the fairly complex rhythmic pattern with its many syncopations and tied notes, but even more so because of the combination of stepwise motion with high melodic tension. The tempo, however, should not be slow since Bach's explicit time signature indicates a pacing in half-note beats.

The appropriate articulation demands legato in all note values, with the exception of the cadential-bass steps mentioned above. There is one detail of the articulation, however, which depends once more on the interpretation of the phrase structure in the subject. For those performers who conceive the subject as consisting of two subphrases, the falling fourth is the only larger interval; it may therefore be played with connected notes, particularly since it comes in strongly ebbing dynamics. For performers who prefer to regard the subject as indivisible, there are two consecutive large leaps to consider, both of which express an active increase in tension; both should then be detached - the first by articulation, the second by the written rest.

Owing to the alla breve indication in the fugue, the relative tempo of the prelude to the fugue is most convincing when it is rendered in complex proportion of 3:2:

an assumed eighth-note triplet

corresponds with
a quarter-note
in the prelude
in the fugue

(Approximate metronome settings: prelude beats = 40, fugue beats = 60.)

The fugue contains only one ornament, the trill in bar 49. It begins on the upper neighbor note, shakes in three pairs of sixteenth-notes and ends with a two-sixteenth-note suffix leading into its resolution on the ensuing downbeat.


I/22.2.6 The design of the fugue

Many of the observations made above in the context of the episodes encourage an exploration of a possible structural symmetry in the fugue. This symmetry is in fact complex but striking; the following table lists the relevant details.

part I (bars 1-36)

part II (bars 37-75)


in v1, v2 S in v2


with ascending M1 E4 with ascending M1
S in v3, v4, v5 S in v3, v5, v1/v2, v4
with gradual ascent
ending in cadential close
  last entry with cadential close
S in v2+v3

with gradual descent
S in v1, v2, v4, v5 S in v1/v2/v3/v4/v5
E3 with cadential close E6 with cadential close

Within each of these two structurally corresponding parts, the entering order of the voices, together with the sense of closure conveyed by some of the episodes, allows two sections to be distinguished. In part I, the layout is straight-forward: section I contains five subject statements linked by a bridging episode (E1) and closed by the cadential formula at the end of E2; section II consists of four entries and the short E3 with its cadential close.

As to the structural boundaries in the second half of the fugue, two conflicting interpretations exist.

In the first concept (which is more in accordance with the rules derived from other Bach fugues), section III, like section I, contains five subject statements, one of which is a stretto; they are linked by a bridging episode (E4) and closed by the cadential formula which accompanies the last entry. Section IV then consists of an initial parallel statement, an episode (E5), the impressing five-part stretto and a final short E6 with its cadential close. The density of the texture supports these findings: sections II and III both commence with only three of the five voices taking part (see bars 25-28: v4 and v5 resting; bars 37-45: v1 and v3 resting); at the beginning of section IV, after a full five-part cadential close in the preceding bars (see bars 53-55), v1 pauses for twelve entire bars.
The second concept builds on the admittedly strong tendency of relaxation in E5, on the structural analogy of this episode with E2 in the first half of the fugue (which is, there, the final segment of the first section), and on the fact that the fourth-voice statement in bars 53-56 overlaps, in its female ending, with the ensuing parallel entry, making it more difficult for both performer and listener to perceive a section ending - and new beginning - here. In terms of the dynamic development, this concept is, no doubt, much easier to effect. In structural terms, however, it not only leaves the fourth section with a single group entry as opposed to two (one parallel, one stretto); it also results in a somewhat unbalanced overall picture (see the following table).


Concept I: sections I II III IV
  bars 1-24 25-36 37-54 55-75
  number of bars 24 12 18 21
Concept II: sections: I II III IV
  bars 1-24 25-36


  number of bars: 24 12 32.5 8.5


As to the harmonic outline of this fugue, it is interesting to observe that it, too, underpins the structure with its four sections in two parts, and with the third and fourth sections as indicated above in "concept I". The initial five subject entries all relate to the home key Bb minor, in the usual alternation of tonic and (minor) dominant position. The second section establishes the subdominant region in its first and last entry; the intermittent statements in Bb therefore appear not so much as the tonic but rather as the dominant to the subdominant. The third section introduces the major-mode version of the subject in its initial statement but soon returns to the subdominant and its dominant. Finally, the fourth section returns to the home key, with the parallel entry in the minor dominant and the five-part stretto in the tonic. (It should be mentioned that the five subject entrances in the stretto pick up the five initial entries in the fugue.)

For a sketch showing the design of the Bb minor fugue see ex. 41.



I/22.2.7 The development of tension

Within the first section, the tension grows steadily; this is due, on the one hand, to the increasing number of voices from one subject statement to the next, and, on the other hand, to the above-mentioned rising pitch outlines in both the bridging E1 and the concluding E2.

Similarly, the texture in the second section expands from three to five voices, adding lower registers as the section progresses. The process, however, is more restricted as regards the growth in the number of voices (3 to 5 vs. 1 to 5 parts) and much shorter in duration (12 vs. 24 bars); thus the impression of increase is not quite as powerful as in the initial section.

The third section not only begins, as the previous one, with two voices resting, but is further transposed to the major mode. The resulting expression is much gentler, particularly since the large leap appears now as a major tenth - an interval with no exceptional inherent tension. The bridging episode, the two single statements and the stretto which follow seem to build up new intensity. Yet several details indicate that the case is somewhat different from the preceding sections. The structural climax in the stretto is offset by the still incomplete texture in these bars; the final statement (see v4: bars 53-56), although now in five-part texture, is not a convincing climax either - both because of its weaker position as a single entry and because of the relaxing tendency in the accompanying closing-formula. Spanning across the confines of this section, this statement is easily heard as conveying the expectancy of something important yet to arise. It is therefore important to notice that Bach postponed the full five-part texture in this section until this entry, and that, by contrast, the subsequent parallel statement together with the long E5 appear in four-part setting only, with the upper voice resting. (This gives rise to a very sensitive question for performers: how does one convey the absence of the top voice when one is in fact playing high pitches?)

The fourth section is thus, under several aspects, the weakest one. It contains only two (group) entries, its build-up of texture is smallest (only from four to five voices), and its episode is the only one in the entire fugue to constitute a protracted decrease of tension. In this regard, the fourth section continues the gradual decline of dynamic power from one section to the other. When the final five-part stretto counter-balances this overall decline by erecting a powerful "super-climax", this should come as a true surprise to the listeners.