WTC I/17 in Ab major -- Prelude

I/17.1.1 The prelude-type

The Ab major prelude is dominated by one motive (see U: bar 1). This motive appears so frequently that, instead of looking for where it occurs one may find it easier to state in which bars it is missing. Of a total of forty-four bars there are only eight (see bars 16, 17, 33, 34, 39, 40, 43, 44) which do not feature the motive. The immediate sequence in bar 2 and the imitation on the octave in bars 3/4 give hints that this prelude may be conceived as an invention.


I/17.1.2 The overall design of the prelude

The first harmonic progression closes on the downbeat of bar 9. The very noticeable interruption indicates clearly that this cadence must be understood as a structural break.

As the regular appearance of the D natural signifies, the next harmonic progression brings a modulation. The target key Eb major is attained after a cadential formula on the downbeat of bar 18. This cadence again marks the end of a structural section.

There are altogether four sections in this prelude:


bars 1- 9d tonic confirmed


bars 9-18d modulation to the dominant
III bars 18-35d modulation back to the tonic
IV bars 35-44 renewed confirmation of the tonic

Several portions in this invention-style prelude recur very faithfully, in only slight transformation:

bars 3-5d recur in bars 18-20d transposed
bars 9-18d recur in bars 26-35d transposed, voices inverted
    (the analogy is only slightly blurred in the closing-formula)
bars 20-22d recur in bars 41-43d transposed

I/17.1.3 Practical considerations for performers

The Ab-major prelude exposes a simple rhythmic pattern based primarily on eighth-notes and sixteenth-notes. With regard to the pitch pattern, the principal motive consists of a broken chord preceded by a written-out inverted mordent; this combination of jumps with ornamental sixteenth-notes can also be found in other components of the motivic material.

The basic character of the piece is thus determined as rather lively. The tempo to express the mood must be fast enough to allow for the ornamental quality of the sixteenth-notes, but not so fast as to deprive the eighth-notes of their spirited character. The corresponding articulation is an effortless non legato for the eighth-notes and quarter-notes, and quasi legato for the sixteenth-notes.

The only exception from this pattern of articulation occurs among the longer note values in U: bars 43/44 where Ab-G-Ab, as one of the typical closing-formulas, must be legato. Within the quasi legato, various shadings of touch are required in order to bring out the different textures. Passages in hidden two-part structure with as background a simple repeated pedal (as in bars 15/16, 32 and 39/40 where weightier and lighter notes alternate regularly) should be distinguished from both those with an ornamented pedal as secondary line (see bars 13/14 and 30/31 where the structural notes are interspersed with feathery inverted mordents) and from the remainder of the sixteenth-note passages in which all notes take part in the melodic line.

The prelude contains two kinds of ornaments, indicated by the same mordent symbol. The two closing-formulas in bars 17/18 and 34/35 each feature the typical interrupted trill (point d'arrêt trill) with anticipation of the resolution note. Both begin on the upper neighbor note and shake in thirty-second-notes (as shown in ex. 45 below). The other four mordent signs, appearing on the quarter-notes in bars 36 and 38 and on the sixteenth-notes in bars 41 and 42 respectively, can be played as just that: three-note mordents which commence on the main note either because they are approached stepwise, as in bars 36 and 38, or because they decorate the initial note of a phrase, as in bars 41 and 42.

(ex. 45)


I/17.1.4 What is happening in this prelude?

The material in this invention-type prelude is dominated by the principal motive. M is one bar long, beginning on the second eighth-note of the first bar and ending with a rest on the downbeat of bar 2. (This rest is later often replaced by a note; however it is vital to state that the original version of the motive omits the downbeat.)

Within this particular metrical structure, the two sixteenth-notes serve as an upbeat to the four eighth-notes; the dynamic presentation should outline this with a little crescendo to the climax on beat 2 and a successive diminuendo to the end, regardless of whether the downbeat is taken up by a rest (as in bars 2, 4, 5 etc.) or by a final note (as e.g. in bar 3 and bars 6-16).

In the course of the composition M appears twice with strictly polyphonic counterparts and twice with accompaniment patterns. Initially it is counteracted by full chords, double notes or octave leaps. All these components, as representatives of homophony in an essentially polyphonic composition, should be kept very much in the background; this is achieved by playing them in neutral tone color, considerably softer than the motive and, wherever they appear extended (as e.g. in bars 3/4 right hand), with beat 2 particularly light. The same applies in the variation of the chordal companion which appears in bars 36 and 38.)

Another basically homophonic accompaniment figure occurs in bars 13/14 and 30/31. This too should be kept in low profile, while the scale descent within the hidden two-part structure in bars 15 and 32 may create a diminuendo which contrasts with the dynamic curve in M.

The other two settings show the principal motive accompanied by what is conceived as a "counter-motive", i.e. a polyphonically independent figure.

CM1 appears in bars 9-12 and 26-29. Its model contains a seven-sixteenth-note upbeat followed by a long downbeat note (see bars 9/10 (U) and 26/27 (L)); in the sequences, the long note is replaced by an ornamental figure (see bars 11/12 (U) and 28/29 (L)). In all cases, the upbeat leads in crescendo to the downbeat which is followed by a decrease through to the fifth sixteenth-note.


also commences with an up-beat in sixteenth-notes (see L: bars 20-22 and 41-43); this is followed, after the climax on the downbeat, by a descending octave jump which provides the relaxation.

Yet another companion appears transitorily. In L: bars 22-24 and U: bars 24-26, M + sequence are contrasted with descending zig-zag figures in continuous diminuendo.

The design of this prelude contains two basically analogous sections, a short middle section and a coda which recalls material from the middle section. The analogous sections appear in the harmonic progressions typical for baroque pieces with recapitulation: the modulation from the tonic to the dominant is answered by one from the subdominant back to the tonic. Details can be seen in the following table.

I A bars 1-9
with chordal
III A' bars 18-20
M with chordal


bars 9-18
M against CM1,
followed by M with
accompaniment figure,
concluded with
cadential formula
(tonic to dominant)


bars 26-35
M against CM1,
followed by M with
accompaniment figure,
concluded with
cadential formula
(subdominant to tonic)


bars 18 - 26
material from A,
(short statement)

  Coda bars 35 - 44
material from A
    followed by
M against CM2
M against transitory figure
    followed by
accompaniment figure
in parallels,
against CM2, and
final cadence.

The tension in each section is determined by three features: the extent of polyphonic contrast, the direction of the sequences, and the harmony.


WTC I/17 in Ab major -- Fugue

I/17.2.1 The subject

Beginning on the second beat of the first bar, the subject of the Ab-major fugue strongly conveys the impression of up-beat. The conclusion after only a single bar therefore comes as a surprise; one is still expecting the main content and is now asked to believe that this was already it. The principal idea of this fugue contains seven regular eighth-notes in all! (Only the final note comes, in the course of the fugue, in a great variety of values, from the sixteenth-note in bar 29 to the dotted half-note in bar 6.) The sensation of incompleteness in this subject is enhanced by the pitch line which features the rather unusual closure on the fifth scale degree, and by the abruptness of the harmonic progression (for details see below).

This short subject is definitely conceived as one indivisible phrase. Its pitch pattern consists almost exclusively of leaps in broken chord setting; only the final note is approached by the interval of a second. The rhythmic structure inside the subject is of the greatest imaginable regularity. The same does not, however, hold true in the remainder of the fugue where the eighth-notes appear mixed with sixteenth-notes, quarter-notes and several syncopated values.

The harmonic background to this subject is certainly somewhat peculiar (ex. 46):

The subdominant is reached on the (metrically weak) fourth beat of bar 1, followed on the downbeat of bar 2 by the dominant-seventh which resolves - melodically inert - on the tied sixteenth-note of beat 2 (see e.g. the harmonization of the statement in bars 5/6). This implies that whenever the final note of a statement is shortened, the resolution may be cut off from the main body of the subject. This is already the case in the answer (see bars 2/3) where the bass is way into the partial sequences which follow this entry when the Eb major resolution of the Bb7 chord appears.

The dynamic outline poses a problem, despite - or perhaps because of - the short range and straightforward character of the subject. On the one hand, the significant features which are (harmonically) the subdominant and (melodically) the highest pitch F coincide; but they fall on a weak beat. On the other hand, the final note, which in the original version holds rhythmic importance through its sudden length, appears so frequently shortened that it may not be entirely convincing as a climax either.


I/17.2.2 The statements of the subject

The fugue contains fifteen subject statements.

1. bars 1/2 T 9. bars 23/24 A
2. bars 2/3 B 10. bars 24/25 S
3. bars 5/6 S 11. bars 27/28 B
4. bars 6/7 A 12. bars 28/29 T
5. bars 10/11 T 13. bars 29/30 A
6. bars 13/14 A 14. bars 30/31 S
7. bars 17/18 T 15. bars 33/34 S
8. bars 18/19 A      

(ex. 47)

The subject does not appear in inversion, stretto or parallel. (Only once, in an episode where the combination of interval and rhythm pattern suggests false entries, does a parallel occur; see bars 21/22 alto/soprano.) The rhythmic variations in the final note and the adjustment in the answer (see the lowering of the second subject note in bars 2 and 6) aside, two interval modifications occur in the statements. Both have considerable harmonic impact.

In bars 18, 28, 29 and 30, an initial fourth interval is followed by the broken triad of bar 1, thus mixing features from original and answer and resulting in harmonic ambiguity. More strikingly, the first three of these entries, which are all in the minor mode, borrow several notes from their major-mode relatives (see bar 18: C + A for Cb + Ab; bar 28: D + B for Db + Bb; bar 29: G for Gb).
Two statements feature a seventh jump instead of the original sixth between the fourth and fifth eighth-note. The result is a seventh chord which now resolves on the ensuing downbeat and thus re-harmonizes the subject as a modulation (see bars 23/24, modulating from Eb to Ab, and bars 24/25, modulating from Ab to Db).


I/17.2.3 The counter-subjects

The Ab-major fugue does not contain a single consistent counter-subject. The sixteenth-note figure which accompanies the subject entry in bars 2/3, while recurring frequently and in much variation throughout the fugue, does not serve as a companion to the subject but provides motivic material which, as in the E-major fugue from the WTC I pervades the entire fugue. (These motives will be portrayed under 5. below).


I/17.2.4 The episodes

The composition encompasses eight subject-free passages.


bars 3 - 5

E5 bars 19 - 23
E2 bars 7 - 10


bars 25 - 27
E3 bars 11 - 13 E7 bars 31 - 33
E4 bars 14 - 16 E8 bars 34 - 35

The material which characterizes these episodes also occurs outside of them, overlapping considerably with the subject but never serving as its dedicated companion. It is most interesting to observe that all this material seems, in one way or another, derived from bars 2/3, i.e. from the first episode and, before it, from the figure which countered the subject's answer. To give more detail, there are three figures which serve as sources for the secondary material. These figures are: the eight sixteenth-notes which follow the original subject statement, the four eighth-notes which extend the answer in the pattern of a partial sequence, and the syncopated half-notes which, with an ornamental variation, sound against this partial sequence. Here are the motives with their variations and a list of their occurrence (ex. 48).

Introduced in bar 2 (T), this motive recurs, with the
opening note displaced to form an ascending scale,
in bar 4 (B). In rhythmic variation with intersected
syncopation is also found in bar 27 (A, imitated in S).
The inversion of M1 appears in bars 2/3 (T), 4/5 (B),
15/16 (A), 22/23 (A) and 25 (T, with two sequences).
This extended version, combining the ascending scale
with the M1 inversion, is found in bars 5/6 (B), 7/8 (A),
8/9 (B), 9/10 (B), 23/24 (T) and 24/25 (T).
An extended version materializes in bars 29/30 (T).

The (free) inversion of the previous motive occurs twice,
in bars 16/17 (S) and 18 (B).


This figure is conceived as a further development from
the same root; the scalar ascent is now complemented,
after a syncopation, by a new tail in eighth-notes. It
occurs in bars 7/8 (B), 8/9 (S), 9/10 (A; here it gives
way to a melodic closing-formula) and in bars 16/17 (B).

A final, now very remote relative combines the scalar
ascent with a subsequent descent. This figure appears
several times, with a varying number of free sequences;
see bars 11-13 (S), 14/15 (B), 19/20 (A) and 31/32 (B).

Introduced as a two-fold partial sequence of the subject,
this motive is introduced in B: bars 3/4 - unfolding here
above an Eb pedal (see Eb-Bb-G-Ab, Eb-Ab-F-G).
It recurs as a separate motive, with occasional ornamental
variation, in bars 11-13 (B), bars 14/15 (A) and bars 19-21 (S).
Also, remote relatives can be heard in bars 25/26 and 31/32.

First presented in the context of M2, this motive could, in fact, be read as a parallel to the M2 peak notes. The consecutive syncopations recur in bars 11-13 (T), 14-16 (S) and 19-21 (T).

The episodes which are most closely related to the subject are those which contain M2, i.e. E1, E3, E4 and E5. More remote variations of this motive in E6 and E7 also convey an impression of relatedness.

The only subject-free passage which serves exclusively as a cadential close is the final one, E8. In addition there is one instance within another episode where the motivic display is suspended and gives way to an extended cadential formula (see bars 20-22, at the end of E5). Two further cadential closes appear more integrated into the motivic material; both contain the typical do-si-do (keynote / leading-note / keynote) figure (see bars 9/10 at the end of E2 and bars 15/16 at the end of E4).

The relationship between the episodes is already evident from the exposure of their motivic content. The first half of E4 and the entire E5 are both direct variations of E3; similarly, E7 is a (more distant) variation of E6.

Only two of the episodes maintain the tension and thus serve as a bridge between subject statements: in E1, a short descent is followed by rising motions, and in E7, the ascending motion in all voices of bars 31/32 is complemented by a relaxation of roughly equal length. All remaining subject-free passages display a pattern of gradually decreasing tension, either because of apparent descending sequences (as in E3, E4, E5 and E6), or in hidden descents (as in E2 where the soprano contains the falling Ab-major scale).


I/17.2.5 Character, tempo, articulation, ornament realization

With the exception of the syncopated half-notes in M3, the rhythmic pattern in this fugue is simple. Moreover, the pitch pattern is most obviously made up of broken chords alternating with ornamental figures. It is thus easy to determine the basic character of this fugue as rather lively (even with, in terms of the spirit expressed in this basic character, the specification "very" lively).

The tempo of this fugue is confined by the character of its primary material. The broken-chord leaps in the subject should sound vigorous (and thus not too slow); the various sixteenth-notes figures should, in view of the manifold motives Bach invented and developed, by no means appear as mere virtuoso patterns (i.e. not too fast).

The corresponding articulation consists of bouncy non legato in the subject and M2, a fairly intense quasi legato in all motives deriving from M1, and a melodious non legato in M3. The only longer note values which must be played in strict legato are the cadential formulas in the soprano parts of bars 15/16, 22/23, 34/35 and in the alto part of bars 9/10. The fugue does not contain any ornaments.

The relative tempo of the swifter and lighter prelude in triple time to the more vigorous fugue in quadruple time is best established by equaling metric, and not rhythmic, values:

one bar

half a bar

in the prelude

in the fugue

(Approximate metronome settings: prelude beats = 120, fugue beats = 80.)


I/17.2.6 The design of the fugue

The most obvious indicators which help determine the design of this fugue are the cadential formulas in bars 9/10, 15/16 and 22/23. As the subject entries preceding the first of these closures constitute a perfect round of all four parts (T B S A), the first section seems thus ascertained. Between the cadential closes in bars 9/10 and 22/23, the striking correspondence of E3 with the first segment of E4 and E5 creates a larger unit from bar 11 to bar 23. The reduction of the ensemble from four to merely two in bars 23/24 further enhances the structural importance of this harmonic closure. Inside this superimposed frame of twelve bars, the closing-formula in the middle of E4 generates a smaller caesura, confirmed in its structural value by the fact that the ensuing subject statement sounds in reduced ensemble (three voices, see bars 17/18).

As no explicit cadential close occurs between bar 23 and the end of the fugue, one has to look for other indicators of structural layout. One hint can be found in the entering order of the voices. The five final statements (B T A S S) seem to form a group: they follow one another not only very closely and in a logical arrangement of gradual ascent, but also lead, after the tension-increasing E7, to the conclusion of the fugue in a redundant soprano statement. The return to the tonic key with the bass entry in bars 27/28 further ascertains the confines of the final section.

The harmonic outline as established in the subject statements and cadential closes confirms the structural layout deduced above. The entire first section remains in the tonic key of Ab major which is substantiated by the cadence in bars 9/10. The second section contains entries in the tonic and its relative minor, and concludes correspondingly with a cadential close in F minor (bars 15/16). The third section sets out in Bb minor and, after the harmonically ambiguous second statement (Bb minor/Eb minor) reaches the dominant key (Eb-major cadence, bars 22/23). The fourth section is characterized by the two modulating subject entries; progressing from Eb via Ab to Db this section approaches the home key from the subdominant region. The beginning of the fifth section, as has already been mentioned, marks the return to Ab major which, though weakened in the harmonically hybrid tenor and alto statements, is not abandoned again.

For a sketch showing the design of the fugue in Ab major see the sketch in ex. 49.


I/17.2.7 The development of tension

The five sections of this fugue present very individual faces.
The first section of the fugue contains the usual build-up of tension created by the gradual increase of the ensemble. While the bridging episode E1 describes a concave curve, with a slight relaxation followed by a new rise preparing the second pair of statements, the section-closing episode E2 with its descending lines brings gradual relaxation.
The second section begins in the tonic key and in four-part texture, but its second entry already represents the minor mode. Thus there is a decrease in tension between the two statements of this section. The two episodes enclosed in the section enhance this tendency of decay. After the cadential close in the middle of E4 the two remaining voices trail along somewhat indecisively.
The two subject statements of the third section with their harmonic ambiguity are not made to bring forth powerful impulses either; the episode E5 which recalls once more the descending sequences already heard in E3 and E4 blends well into this picture of "no news, no emotional features". The explicit cadential formula thus appears as the closure of a protracted decline, summing up the sections I, II and III as one large portion.
The fourth section commences with the lowest number of voices found in a statement outside the initial one and represents a correspondingly reduced level of intensity. However, the particular harmonic design of the two subject entries as modulating statements, together with the fact that they bring forth the return to the home key of the piece, endows this section with considerable urge.

Although mollified transitorily during the episode, this urge continues even more powerfully in the four consecutive statements which mark the beginning of the fifth section. The ensuing episode E7 is characteristically the only tension-sustaining one apart from the very first episode. After its deceptive cadence (see bar 33 beats 2/3), the final statement sounds in an almost homophonic setting, giving the fugue a triumphant closure.