WTC II/17 in Ab major - Prelude

II/17.1.1 The prelude-type

This prelude is based on several motives. Some of them are used in imitation and with many modifications typical in polyphonic material; others are presented with a distinct accompaniment or, with an answering motive in the other voice. The texture is conceived in two polyphonic parts both of which split regularly to form chordal patterns.


II/17.1.2 The overall design of the prelude

The first harmonic progression ends with the confirmation of the home key on the downbeat of bar 7. This close marks a structurally relevant point. In view of the large-scale design of the prelude, however, one might prefer to call this the end of a sub-section since the more convincing section ending appears, complete with cadential formula, in bars 16/17.

The prelude comprises five sections:

bars 1-17d
tonic to dominant (Ab major to Eb major)
(bars 1-7: tonic confirmed, 7-17d: modulation
bars 17-34d dominant to tonic relative (Eb major to F minor)
(bars 17-23d: dominant confirmed, 23-34d: modulation)
III bars 34-50d tonic relative to subdominant (F minor to Db major)
(bars 34-40d: tonic relative confirmed; 40-50: modulation)
bars 50-64d subdominant to tonic (Db major to Av major)
(bars 50-632: modulation, 632-64d: retransition) 
bars 64-77 tonic confirmed

There are extended structural analogies in this piece.

bars 1-4 recur in bars 17-20, 34-37
(transposed and varied)
bars 1/2 recur in bars 50/51
bars 5/6 recur in bars 21/22, 38/39 (transposed and varied)
bars 7-9d recur in bars 40-42d (transposed and varied)
bars 11-17d recur in bars 44-50d (transposed and varied)


II/17.1.3 Practical considerations for performers

The basic character of this prelude is rather calm. Rhythmic patterns are complex, containing a large variety of values from dotted and tied eighth-notes to thirty-second-notes. Clearly the main rhythmic feature is the long on-beat note followed shortly before the next beat by one, two or three fast notes. This gives the piece a swinging momentum which prevents too slow a tempo.

The articulation is mainly legato. Most of the interval jumps occur either inside sixteenth-note patterns or between thirty-second-notes and the following longer note, i.e. in instances where detached playing is ruled out. The indicated wedges in bars 5/6 which specifically demand abbreviation of the long notes make it clear that in this piece, the dotted notes are generally meant to be taken legato. As with all indications regarding articulation or ornamentation within thematic material, this wedge should be transfer red to corresponding notes. This applies clearly to the G in bar 393; whether the same holds true for the Ab in bar 213 depends on the individual performer's interpretation of this bar - which may or may not be perceived as deriving from bar 5.

Conventional exceptions from the general legato touch occur in cadential-bass patterns (see bars 16, 33, 49, 62 and 74). Other exceptions, in which articulation is explicitly marked, also occur outside the main thematic material in cadential context. In bar 62, paired slurring indicates dynamic shading in an active-passive pattern (these slurs reinforce the harmonic feature of appoggiatura-resolution, rather than indicating an abbreviation of the second note). In bar 76, the slur which links the quarter-note Ab to the subsequent G might well serve as a preventive measure: to guard against any possible interruption of the final closing-formula.

The Ab-major prelude contains three types of ornaments: several mordents, an inverted mordent and grace-notes. Mordents occur in two different contexts. The first (see bars 52-59) represents a thematically integrated ornament appearing before the backdrop of regular sixteenth-notes in the accompaniment. Each of these mordents is approached in stepwise motion, begins therefore on the main note and contains only a single three-note shake. The second type of mordent (see bar 76) is a cadential ornament. As it appears with no other rhythmic features against it and marks the essential step in the final ritardando, this mordent can be more elaborate. Commencing equally on the main note, it may contain two or three shakes (i.e. five or seven notes) before it stops short.

The inverted mordent marks the cadential-bass pattern immediately preceding the final homophonic formula (see bar 743). In accordance with the harmonic context given by the bar it must be played with Cb as its lower neighbor note.

The two grace-notes in this prelude both occur in bar 75, as part of the final homophonic cadence; both are indicated as eighth-note appoggiaturas to a main note of quarter-note value. In both cases, the graces are thus played on the beat, together with the chordal notes in the right hand and the bass notes, and resolve after one eighth-note into the harmonically awaited notes G and Eb respectively.


II/17.1.4 What is happening in this prelude

The variety of motivic material in this prelude allows for various concepts - and thus various ways of labeling. On the one hand, distinction of all similar but not-quite-identical shapes would lead to so large a number of individual shapes that performers as well as listeners risk losing track; the benefit of an analysis would thus be thwarted. On the other hand, recognizing too many different shapes as variations of a single idea might become meaningless.

The following discussion tries to eschew both traps by taking into consideration not only the actual appearance of a melodic unit but also its texture and context.

M1 is presented in bars 1-2d. It consists of two manifestations of the broken chord.
  * In the left-hand part, a descending Ab-major chord appears in a linear pattern (M1a). The skips are not bridged by the fast notes which follow the dotted strong-beat notes but, on the contrary, widened as the sixteenth-note-pairs each time run up to the next higher note of the same chord; thus Ab-Eb-C-Ab appears as Ab--(C) Eb--(Ab)C--(Eb) Ab.
  * Its homophonic accompaniment (M1b) presents the Ab-major chord in a pattern which focuses on off-beat block chords preceded by auxiliary notes in the keynote / leading-note / keynote pattern.
  Dynamically, M1 describes a decrease in tension; this is caused by the repetitive effect of M1a and the absence of any harmonic activity in this motive and enhanced by the descending direction of the melodic part M1b.
M1 recurs very similarly in bars 3, 17, 19, 34, 36 and 50. A variation can further be found in bar 10. Moreover, the accompaniment M1b appears separately and in slight variation in bars 52, 54, 56, 58 and 59. It is worth noticing that the motive and its recurrences do not include any imitation or inversion of voices: the melodic line always remains in the left-hand part and the accompanying chords are restricted to the right-hand part.


is an almost ubiquitous figure in this piece. Introduced in bar 2 and appearing in a variety of pitch patterns, its discerning feature is the rhythmic pattern which consists of regular sixteenth-notes beginning after a downbeat rest and ending on the next downbeat.
All variants of this motive share the dynamic layout which entails an initial crescendo to beat 2 followed by a gradual relaxation until the downbeat. These are its shapes:



M2a consists of an initial "turn-figure" followed by a broken chord (in various shapes) and a descending scale. Introduced in bar 2 where it is particularly noticeable as it sounds against rests in the left-hand part, this version of the motive recurs in bars 4, 18, 20, 35 and 51.

M2b combines the same beginning with an ascending scale; it occurs in bars 5/6, 21/22 and 38/39. (Its accompaniment, beginning like all variants of M2 with the characteristic "turn", is retained in bars 6, 21 and 39 only.) A single irregular modification can be found in bar 37.

* M2c looks like a wavy line but can be read as an ornamented descent, with escape notes reminiscent of the broken-chord patterns typical in this prelude. This version is introduced in U: bar 7 (Eb turn/ Eb-Db-C/C-Bb-Ab); it recurs in U: bars 8/9, 29-31, 40-43, 68, 70-73 and in L: bars 24, 26, 28, 32, 65, 67, 69.
* M2d begins similarly but contains a conspicuous high-tension interval-jump (minor seventh); see bars 23 and 25, 64 and 66. M2e stands out for its zig-zagging shape; see bars 53, 55, 60.
* A more surprising variation is M2f, introduced in bars 112-122. Omitting the initial turn-figure, it begins with a broken chord and scalar descent which are complemented with an ornamented broken chord on the following downbeat. This metrical shift induces a change in the dynamic design which now demands continuous crescendo. The motive is sequenced (see bars 12-15) and recurs, slightly further varied, in bars 44-48.
  In contrast to M1 which remains confined to its initially homophonic setting, M2 is polyphonic, changes voices and joins a number of other motives.

M3 also shows many facets. It first appears in the lower part of bars 7-8d.
* M3a, the original version, consists of a three-thirty-second-note upbeat followed by a scalar descent in dotted rhythm. As in M2, the dynamic climax in M3 also falls on beat 2. The motive is sequenced in bars 8-9d and 9-10d and recurs in a slightly more extended chain of sequences in bars 40-44d. In all cases, M3a is accompanied by M2c.
* M3b, a first variation, appears in bars 12-13d. Beginning with a run similar to that in M3a, this variation continues with a figure in dotted rhythm but changes the simple ascent to a zig-zagging line. M3b is sequenced in bars 13-15d; a closely related variant appears in bars 45-46d, with sequences in bars 46-48d, and the original shape of M3b recurs in bars 64-65d and 66-67d.. In the latter cases, M3b is accompanied by M2d.
* M3c, another variation of the same basic figure, retains the dotted-note descent but ornaments it and modifies the harmonic foundation of the motive; this occurs in bars 52-60d. The accompaniment is alternately a variation of M1b and M2e.
* Finally, M3d is most removed from the original as it lacks the dotted rhythm in the second half. Here, the initial run is continued through the figure in two internal sequences which end in an abrupt and dramatic jump of a minor seventh (see bars 23-24d). Due to this high-tension interval, the dynamic layout of the motive changes into a continuous one-bar crescendo. This variant recurs in bars 25-26d, 27-28d and in partial quotations in bars 29-33; it is taken up again and varied further in bars 65-66d, 76-69d, 70-74d. The accompaniment is provided by either M2c or M2d.
M4 differs from the three previously mentioned motives in that it is chordal and not linear (see bars 24-25d). It is thus closely related to the homophonic accompaniment within M1. This motive appears not as an active component in its own right but as a complement to M3c, which thus becomes a two-bar figure and only drops this complement in the liquidation process from bar 29 onwards.

The following table attempts to give an overview of the structural design in the prelude as it results from the interplay of the three motives and their variations. This chart also clearly shows the basic analogy between the first three sections.

Section I Section II Section III
M1a/M1b + M2a M1a/M1b + M2a M1a/M1b + M2a
M1a/M1b + M2a M1a/M1b + M2a M1a/M1b + M2a var
M2b/M2b var M2b/M2b var M2b/M2b var.
M3a/M2c + sequ. M3d/M2d, M4/M2c + sequ. M3a/M2c + sequ.
M3b/M2f + sequ. M3d/M2c + sequ.+liquidation M3b/M2f + sequ.
Section IV

Section V

M1a/M1b M3b/M2d, M3d/M2c + sequ.
M2a M4 var/M2c var
M3c/M1b, M3c/M2e + sequ. M3d/M2c + sequ.
extended cadence + link extended cadence


WTC II/17 in Ab major - Fugue

II/17.2.1 The subject

The subject of the Ab major fugue spans exactly two bars. Beginning after a eighth-note rest on the fifth scale degree (Eb), the phrase reaches the cadential conclusion on the downbeat of bar 3, in a gentle ending with the third degree of the scale (see bar 3d: C). The harmonic background is basically simple. Its most significant feature is the progression from the sub dominant to the dominant in the course of the syncopation (ex. 50):

The rhythmic variety within the subject comprises eighth-notes, sixteenth-notes and a syncopation of five-sixteenth-note duration. Later in the course of the fugue, quarter-notes are added as regular features. Yet despite the presence of these four different note values, the overall impression in the fugue is one of rhythmic simplicity. This impression is due primarily to the fact that the sixteenth-note pulse, once firmly established in the second half of the subject's answer, provides an almost continuous motion until the general pause in bar 46. (In fact, all through these forty-two bars the sixteenth-note motion only "misses" four beats: one each in bars 13, 14, 16 and 19.)

The subject's pitch pattern features a number of consecutive jumps - three of them at the very beginning in increasing interval span (third + fourth + fifth) and two more (octave + fourth) before the downbeat of bar 2. The two ascending tetrachords (see bar 1: Bb-C-Db-Eb, bar 2: Ab-Bb-C-Db) constitute, particularly in this rhythmic shape, popular formulas often interpreted as bridged fourth-jumps. Finally, the sixteenth-note figure filling the second half of bar 2 has ornamental character, embellishing the suspended resolution Db-C.

It might be interesting to visualize the bare skeleton of this subject, stripped of all its ornaments (including, for this purpose, the octave split). What emerges is a shape striking with regard to both its interval pattern and its rhythm: the subject turns out to be based on a progression of ascending fourths and descending fifths, unfolding in a pattern of gradual rhythmic augmentation (ex. 51):

The phrase structure in the subject can be interpreted in two ways, depending on whether one chooses to emphasize some of the subject's structural details or its harmonic and rhythmic features.

(a) On the one hand, one could wish to stress the fact that the tetrachord at the outset of bar 2 is a sequence of that in the second half of bar 1.
In this case, one can render the subject as consisting of two subphrases, divided by the octave jump. Its phrase structure may then be described as
* three-eighth-note upbeat + ascent 1
* one-eighth-note upbeat + ascent 2 + tail (ornamented resolution)


On the other hand, one could regard as the subject's salient feature the syncopation in bar 2. This note is not only metrically important but also harmonic ally prominent because its tied sixteenth-note represents the progression from IV to V. In this case, the subject would be rendered as an undivided unit encompassing two consecutive upward thrusts which peak in the syncopation.

The dynamic design differs accordingly.

(a) If the emphasis is on the two tetrachords, the three-eighth-note upbeat leads to a first climax on Bb, followed by a decrease on the way up to Eb. The lower Eb provides the active upbeat to the second climax on the Ab which launches a gradual relaxation throughout bar 2 to the final C.
(b) If the emphasis is on the syncopation, there is only one climax, reached in one unbroken crescendo and followed by a diminuendo of almost equal length.

Especially for a lively interpretation of this fugue, the second option for phrasing and dynamic shaping is clearly preferable.


II/17.2.2 The statements of the subject

We can count fifteen subject statements.

1. bars 1- 3 A 8. bars 22-24 S
2. bars 3- 5 S 9. bars 24-26 A
3. bars 6- 8 T 10. bars 32-34 T
4. bars 8-10 B 11. bars 35-37 S
5. bars 13-15 B 12. bars 37-39 B
6. bars 16-18 A 13. bars 41-43 T
7. bars 18-20 T 14. bars 42-44 (45) B
      15. bars 48-50 T
(ex. 52)

In addition to the adjustment of the initial interval in the tonal answer, the subject suffers several minor changes. The fourth and fifth as well as the eleventh and twelfth statements end on the keynote instead of the third degree. This is a modification frequently used by Bach for bass statements (as in three of the cases here), so the only surprise is that in this fugue it also appears once in the soprano (see bars 36/37). Furthermore, two statements feature an artificial leading-note in the first tetrachord which is later corrected (see B bar 14 and T bar 41: D natural instead of Db). The final statement, while difficult to read (and hear), appears as an unmodified answer.

More significant modifications occur in bars 42-44. The bass entry not only overlaps with the preceding tenor entry for half a bar, but also features drastic harmonic alterations which transpose its final half bar into the key of Db minor. The final note of the subject does not, however, provide the expected resolution, so that the partial sequence which follows must be regarded as an integral part of this entry. On the downbeat of bar 45, this extended subject statement concludes with an interrupted cadence (the Bbb major chord is VI of Db minor). Similar but not quite so drastic harmonic alterations occur in the bass statement of bars 37-39. Commencing as an implied Db-major entry, the sudden Fbs towards the end suggest a turn towards Db minor. (The final chord, due to confirm this key, appears however accompanied by an unresolved voice and allows for subsequent modulations, here again wrapped into a partial sequence; see beat 4 of bar 39 the closing-formula in the soprano leading to a resolution in Ab minor. More on this in paragraph 8 on episodes.)


II/17.2.3 The counter-subjects

Bach has endowed this fugue with two counter-subjects. The first (CS1) accompanies all statements of the subject except the initial one. In two cases, CS1 is reduced to only its tail. As the structural analysis will show, this underscores the position these subject entries occupy in the design of the fugue. The second counter-subject (CS2) displays its first slight variation already in its second statement. Further recurrences continue the process of variation and modification so radically that it then seems no longer meaningful to use the same name.


is introduced in the alto against the subject answer (see bars 3-5: Eb-Eb). It is launched by a six-note chromatic descent in regular quarter-note motion and concludes with a keynote / leading-note / keynote formula in the typical rhythmic pattern. In the first statement of CS1, the quarter-note descent is preceded by a three-sixteenth-note group linking the end of the subject entry to the beginning of the counter-subject. This link, however, is not a consistent feature in the further course of the fugue; it recurs only twice (see bars 8 and 41).
The dynamic outline of this counter-subject follows its salient features. The first and main climax falls on the initial quarter-note and launches a gradual decrease through the chromatic descent. A secondary climax marks the syncopation in the closing-formula. These two diminuendo gestures build a powerful contrast to the crescendo which prevails throughout much of the subject.
CS1 experiences one frequent and important alteration which leads to a harmonically unresolved conclusion of the subject entry: the leading-note in the closing-formula is either suspended (see bar 15: S and bars 23/24: T), flattened and suspended (see bar 20: A and bar 26: S), or flattened and continued downwards (see bars 36/37.) In bars 15 and 23/24, in addition, CS1 swaps voices: its chromatic descent sets out in the tenor and bass respectively while the closing-formula switches to soprano and tenor. Smaller variations are the ornamentation of the chromatic descent which appears in bars 41-44 (S). Finally, the entire closing group of CS1 is omitted in bars 38/39, 42/43 and 50, while the closing group appears alone, without the initial chromatic descent, in bars 33/34 (A) and in bar 18 (B).

CS2 is introduced also in the alto, in its regular position against the third subject statement. It consists of a long stream of ornamental sixteenth-notes followed by four eighth-notes (see bars 6-8d). Varied recurrences can be found in bars 8-10 (S), bars 22-24 (T switching to B) and bars 24-26. (Very generous analysts also recognize it in the soprano of bars 32-34 and in the alto of bars 37-39.) In its pitch pattern and phrase structure, CS2 is conceived as a hidden parallel to CS1 (see the example below) and therefore represents no independent dynamic gesture.

The example shows the dynamic development and the phrase structure in the primary material of the Ab-major fugue (ex. 53). The subject is depicted here as unphrased. Performers who prefer the other option can easily modify the sketch accordingly.


II/17.2.4 The episodes

The Ab-major fugue contains eight subject-free passages.

E1 bars 5 - 6d E5 bars 26 - 32d
E2 bars 10 - 13m E6 bars 34 - 35d
E3 bars 15m- 16m E7 bars 39 - 41d
E4 bars 20m- 22d E8 bars 45 - 48m

Two of these episodes need to be further divided. E5 encompasses a cadential close in C minor which partitions E5a (bars 26-27m) from E5b (bars 27m-32d). In E8, the two halves are separated conspicuously by the general pause on the middle beat of bar 46.

Looking at the melodic features in the episodes, we find material derived from the subject and the counter-subject as well as independent motives.

(a) The subject's head appears in six-eighth-note and four-eighth-note length; in all cases, the fragment precedes an immediately following subject entry; see:


A: bar 5, preceding a tenor statement;


A: bar 34 and S: bars 34/35, with modified interval structure, preceding a soprano statement;

B: bars 20m-21d, in even more strongly modified interval structure, preceding with two sequences, a soprano statement.

(b) The subject's sixteenth-note-tail occurs both as sequence and imitation; see:
E3 two imitations in T: bars 15/16, and in B: bar 16;


three imitations in A: bars 20/21, T: bar 21, and A: bars 21/22;


three sequences in A: bars 26, 26/27, 27;


two sequences in T: bars 34, 34/35 (both considerably altered);

two sequences in B: bars 39, 39/40 followed by
two imitations in S: bar 40 and A: bars 40/41.


The modified closing-formula of the counter-subject appears in one episode:


three sequences in T: bars 20/21, in A: bar 21, and in T: bars 21/22.

is introduced in E1 (see S bar 5: F-Ab) where it is followed by a free extension. With its eight-sixteenth-note figure, it recalls the subject's tail. The motive recurs in:


B: bar 10, with six sequences in bars 10m-13m;

S: bars 27/28, with two sequences in bars 28-29d, followed by an
imitation with two sequences in A: bars 29-30m and
an imitation with two sequences in B: bars 30m-32d.


is first heard in E2 (see S bars 10-11m: Bb-C). With its chromatic steps, it contains a certain allusion to CS1. Its initial fourth jump and the following half-note, however, set the motive distinctly apart, as does the ornamental scale which fills the final chromatic step Db-C. This motive recurs in:


sequenced in A: bars 11m-13d (partial sequence in S: bar 13);

re-established in B: bars 27m-29d, with two imitations in S: bars 29-30m and A: bars 30m-32d.

M3 acts as the contrapuntal companion to M2. It appears in:


A: bars 10-11d, imitated in S: bars 11-12m;


A: bars 27-28m, imitated in B: bars 29m-30d and in S: bars 30-31m.

Cadential closes materialize in three of the episodes. There are two progressions which, complete with closing-formulas, provide perfect cadences: E3 concludes in F minor on the middle beat of bar 17 (keynote / leading-note / keynote in S), and E5a is marked by a cadence in C minor which terminates, after a cadential-bass pattern, on the middle beat of bar 27.

E8 is the only episode not to use any of the previously introduced motivic material. A largely homophonic texture sets it apart from the remainder of the fugue. In E8a, a broken-chord figure in the bass accompanies metric block chords in a harmonic progression from Bbb major to Eb9. E8b follows with a two-part texture in contrary-motion scales which reconfirm Ab major. These lead, in bar 48, into another homophonic pattern which ends, on the middle beat of bar 48, in an interrupted cadence (F minor chord).

Another episode needs more detailed observation. In E7, the unresolved Db-minor cadence of the subject entry is "corrected", half a bar later with an explicit formula in the soprano, in favor of Ab minor (see bar 39 beat 4). Yet neither the harmonic progression nor the episode end here. The following sequence of the subject's tail leads into Eb minor (beat 2 of bar 40) which is then modified, in a thinned texture and without any enhancing formulas, to Eb major, the dominant of the home key.

The relationship between the episodes becomes obvious from what has been said.

- E2 and E5b are completely self-contained, exposing exclusively the three independent motives;
- E1 and E6 share the combination of the subject-head with a sixteenth-note figure, as well as an equal length of only one bar;
- E3 and E5a both conclude the preceding development, after several quotations of the subject's tail, with a perfect cadence.

The role played by the episodes in the development of tension can be described as follows:

E1 and E6 both bridge between consecutive entries. Due to the prominent appearance of the subject's head, the level of tension falls only slightly back from that of the subject statements and rises again for the subsequent entry.
E2 and E5b are on a plane entirely different from that of the subject statements and the other episodes. Therefore, these two passages are best distinguished from their surroundings by a clearly different tone color and touch. Beginning softly, the constantly rising sequences of M1 suggest a gradual increase in tension. In E5b, the progression of the M1 sequences seems, at first glance, interrupted by the double change of voice and register. Note, however, that in both cases (bar 29d and bar 30m) the pitch progression is continued logically an octave lower. The dynamic increase should take this into consideration and be as smooth and unbroken as possible.

E3 and E5a

pick up the tension remaining at the end of the preceding subject statement which, due to the unresolved counter-subject ending, has not reached complete relaxation. The two episodes then continue and complete the dynamic decline. Similarly, the falling sequences of the subject's tail in E7, together with the one-by-one drop out of voices and the harmonic resolution, also generate the effect of closure.

E4 and E8

are the only subject-free passages to create an increase in tension. In E4, the basic intensity is guaranteed by the choice of episode material which stems here exclusively from the subject and counter-subject. A very gradual dynamic growth is induced by the rising direction of the sequences and imitations. In E8, by contrast, the change of texture from dense four-part polyphony to homophony, together with the contrary motion and the impact of the harmonic step from Bbb major to Eb9 creates a strong and sudden outbreak of almost virtuoso quality. After the general pause, E8b begins with only two voices on a much softer level. A renewed build-up, again provoked by contrary motion, proceeds only until the middle beat of bar 47 after which the tension declines throughout the preparation for the cadential close. The fugue ends on a particularly soft note as the expected resolution is deceived by an interrupted cadence.


II/17.2.5 Character, tempo, articulation, ornament realization

Due to the overall effect of rhythmic simplicity, combined with the predominance of interval jumps and ornamental sixteenth-notes in the pitch pattern, the basic character of this fugue must be interpreted as rather lively. The tempo should not, however, be too swift, both in order to avoid the superficial effect of runs without melodic contours in the sixteenth-notes, and to allow the listener to fully appreciate the melodic closing-formulas and their occasional deflection in an additional syncopation (see the end of the counter-subject, from bar 15 onwards).

Due to the greatly different character and mood of this prelude and fugue, the relative tempo of the two pieces can be taken in simple proportion without risk of dullness.

one eighth-note
corresponds with

one quarter-note

in the prelude
in the fugue
(Approximate metronome settings: prelude beats = 44, fugue beats = 88.)

The articulation demands very careful nuances. (Distinctions may seem small and, particularly to impatient performers, hardly worth the effort. Yet they do make all the difference in this fugue where color contrasts - between subject and counter-subject on the one hand and between primary material and independent episode material on the other hand - are essential.)

The shortest and most energetically bouncing non legato is the one found in those eighth-notes of the subject which do not form part of an ornamental tetrachord. (To avoid confusion, here is the articulation in the subject: Eb C F non legato, Bb until Eb legato, both Ebs non legato, Ab until Db and all remaining sixteenth-notes legato.)
A not quite so energetic - and therefore slightly longer - non legato applies in the cadential-bass patterns and in other non-melodic eighth-notes in cadential style (see B bars 15 Ab-C-Db-Ab, 20 G-Ab-Db-Eb-Ab, 26/27 Bb-Eb, Ab-D-F-G-G-C, and bars 47m-50, all eighth-notes and quarter-notes).
An only very gently detached non legato is appropriate for the chromatic descent in the counter-subject.
The eighth-note jumps in M3 should aim to express a color different from those in the subject. While they may sound equally short, their character is certainly much lighter, and graceful rather than energetic. The same applies to the initial fourth in M2.
The chromatic descent in M2 can be taken either in very dense non legato or, perhaps preferable in view of the attempted color contrast, in legato.
All melodic formulas are legato. This applies, as was already mentioned, to the two rising tetrachords in the subject, the closing-formula in the counter-subject, and the cadential formulas in S bars 16 (F-E-F), 39 (Ab-G-Ab), 44/45 (Db-C-Db) and 50 (Ab-G-Ab). Wherever the closing-formula at the end of the counter-subject is deflected, it should nevertheless retain the legato distinction to clearly mark its melodic origins (see bars 15 S, 18 B, 20 A with imitations in T/A/T, 23 T, 25 S, 36/37 A).
While the sixteenth-notes in the subject which are ornamental in origin are perfectly linked, those in M1 and M2 gain extra color distinction if played very lightly, with a crisp quasi-legato touch.

There is only one ornament: the cadential trill in bar 48 (S). It begins regularly from the upper neighbor note, shakes in thirty-second-notes and ends without any rhythmic interruption in the suffix spelled out by Bach.


II/17.2.6 The design of the fugue

The structural layout of this fugue is easy to grasp. The entering order of the subject statements, combined with cadential endings followed invariably by reductions in the number of voices create a particularly unambiguous design, the only irregularity consisting in the position of an episode at the beginning of a section. These are the details:

The first section comprises the original round of four subject statements (A S T B) connected by E1, followed by the (self-contained) E2, a redundant entry in the bass and the closing E3. While all five entries are in the key of Ab major, in regular alternation between tonic and dominant, the closing episode modulates to the relative minor key and concludes the section on the middle beat of bar 16.
Section II contains four subject statements as well as E4 in their middle, i.e. the episode which was analyzed as closest to the thematic material. The beginning of this section is clearly underpinned by the reduction of the ensemble to only two voices (see bars 16m-18m). Harmonically, the subject statements return once more to the home key and repeat the modulation to F minor, this time in the final entry. This alto statement is conceived as redundant in the round (A T S A) and thus announces the pending end of the section which is confirmed in E5a with the cadential close in C minor.
The third section commences with a subject-free passage of almost five bars (E5b). This is followed by three subject statements (T S B) linked by E6 and closed by E7. Harmonically, all three entries are in minor mode (Eb minor, Bb minor and Db minor, representing the minor dominant, the relative of the subdominant and the minor subdominant respectively).
The return to the home key, prepared in the modulatory process in E7 and confirmed with the tenor entry in bar 41, marks the beginning of the fourth section. This section encompasses three subject statements, the last of which is conceived, for the third time in this fugue, as a redundant entry (T B T). The harmonic digression at the end of the bass entry and in the subsequent E8 enhances the impression of redundancy and thus gives the fugue a particularly well-rounded ending. This section is distinguished from the preceding ones not only by its different use of texture - with virtuoso patterns in one hand and block chords in the other, rhythmic surprise in the weak-beat general pause, and a four-part cadence with interrupted close - but also by particularities of its internal structure. The four opening bars feature the only overlap of subject statements in the fugue. The counter-subject of both entries involved in the stretto is varied and merged into a single prolonged chromatic descent (see bar 41 Ab to bar 44 Bb), and the bass entry is extended up to the downbeat of bar 45. The impression arising is that of a superimposed four-bar phrase.

For a sketch showing the design of the fugue in Ab major see ex. 54.


II/17.2.7 The overall dynamic outline of the fugue

The first and second sections are moderate and fairly similar with regard to their overall intensity level, while the third section with its consistent harmonization in the minor mode appears comparatively subdued, and the fourth section is even more outgoing than the opening.

Within section I there is a gradual increase of tension due to the growth in the number of voices. E1 constitutes only a short lessening of tension without any serious interruption in the dynamic build-up from one subject entry to another. E2, however, as was expounded above, brings with it a fundamental change of color as well as, at the outset of the episode, a radical drop in tension. While the ascending sequences of M1 generate a certain increase, the redundant bass entry sounds considerably less assertive than its predecessors, last but not least because, abandoned by the alto, it is left in three-part setting.

Section II repeats the process with different means. Commencing in unusually reduced ensemble and thus almost as softly as the first section, the build-up of tension proceeds unhampered through three entries linked by the intense E4. The last entry of this round resembles that of the previous section in that it is both redundant and set in three-part texture. The harmonization in minor completes the picture, so that section II also ends on a softer note.

What was left out in these two otherwise almost analogous sections, the self-contained episode, is now made up for at the beginning of section III. Commencing very softly, this episode engenders a very gentle increase of tension. The three subject statements then continue this development in a line which is only transitorily suspended during E6. After the - still very moderate - climax in the bass entry, E7 provides both dynamic relaxation and release from the minor mode.

Section IV, finally, begins with a boost of confidence, in a three-part major-mode entry. The harmonic digression mentioned above provokes the climax not only of this section but of the entire fugue in bar 46, followed by the softer curve of E8a and the triumphant five-part final statement.