Prelude {{Listen|type=music Although
Philipp Spitta has seen elements of northern traditions of the early Prelude BWV 543a/1 typical of the school of
Buxtehude, has pointed out that the same features are also present in the later version BWV 543/1. These include solo passages at the start; semiquaver passages with hidden two- or three-part counterpoint in both the manuals and pedals; virtuosic demisemiquaver passages with trills leading to a cadence; and running semiquaver and demisemiquaver figures throughout, including at the start and in the coda. The traditional aspects are the semiquaver arpeggiated passage work with its "latent counterpoint" which incorporates a descending
chromatic bass line. The semiquaver figures begin as a solo in the manual: : and then, after a lengthy demisemiquaver embellishment over a tonic pedal point, are heard again in the pedal. The highly embellished cadence that follows—full of manual runs over sustained pedal notes—leads into a contrapuntal exploration of the opening material in
sequence; this is followed by a very free peroration. Features which distinguish Bach's writing from seventeenth-century compositions include its regular tempo throughout; the careful planning of climaxes; the well-judged changes from semiquavers, to semiquaver triplets and then demisemiquavers. After bars 36, there are semiquaver motifs in the manuals answered by similar motifs in the pedals: there are
brisé effects similar to those found in chorale prelude
BWV 599 or the
Passacaglia, BWV 582/1; and pedal motifs similar to those found in the chorale prelude
BWV 643. For both of these chorale preludes from the
Orgelbüchlein, however, it is the systematic use of motifs that establish a particular musical mood. The
Toccata-like Prelude in A minor—in the
stylus phantasticus—bears the hallmarks of Bach's early, north German-influenced style, while the
fugue could be considered a later product of Bach's maturity.
Fugue {{Listen|type=music The versions of the 4-part fugue for BWV 543a and BWV 543 are identical; it lasts 151 bars. The theme can be traced back to Bach's organ concerto in A minor
BWV 593, transcribed for
organ from
Antonio Vivaldi's concerto for two violins, Op.3, No.8, RV 522, part of his collection ''
L'estro armonico.'' The fugue can be broken up into sections as follows: •
Bars 1–30. There is an exposition for each of the four parts, three in the manuals and one in the pedal, each lasting four and a half bars with a connecting half bar. The main subject starts with a
head-motif which is curtailed by descending sequential arpeggiated figures. There is also a simultaneous
countersubject in response to the new fugal entries. After the entries by the two higher voices, there is an episode in bars 11–14 as a
codetta, heralding the first entry of the lower manual part. There is a similar six and a half bar codetta before the pedal entry sounds, but now the subject is off kilter, with the pedal entry starting on the off beat. •
Bars 31–50. There is a four and half bar episode, developing the exposition, with the 3 manual parts in the countersubject and busy arpeggiated sequences in the pedals. The lower manual part then remains silent, as new freely developed thematic material begins: first in parallel sixth semiquavers in the upper manuals accompanied by quaver motifs in the pedals; and then with briefly semiquaver motifs in the pedals before a three bar trio between the upper parts and pedal, leading to a
hemiola with a cadence on the tonic A minor (thus, in the baroque musical style, two beats of
time are replaced by three beats of
time, ornamented on the last beat for the cadence). The highest part now sounds the fugal theme, with simple accompaniment from motifs in the other upper manual part and the pedal: their trio is truncated by a further hemiola with ornamental cadence. •
Bars 51–61. The lowest manual part enters in the dominant key, with a disguised version of the head-motif of the fugal theme. The pedal part remains silent, while, led by the lowest manual parts, the upper parts together play "
circle of fifths": baroque musical sequences, with successions of harmonies that at each stage progress from dominant to tonic (or tonic to dominant). •
Bars 61–95. This passage, for keyboard alone, is a new restatement of the fugue theme in C major, the relative major. The manual entry is
en taille, from the French "in the waist," a tenor voice often played on a
tierce or
cromorne organ stop. In this case the fugal entry plays between the highest and lowest parts on the manuals. There is then an episode involving circle of fifths; an answering entry on bar 71 in the highest part; a pedal point in the lowest manual part, above a circle of fifths episode; and finally, as the lowest part is silenced, a duet between the upper parts, with a further restatement of the fugal theme in the lower part followed by another circle of fifths episode. •
Bars 95–135. The first bars of this section involve a
stretto passage: the pedal starts to play the fugue theme as usual, only to be taken up by the true fugue theme, off the beat and in the lowest manual part. Between bars 113 and 115, there is a further fugal entry in E minor in the middle manual part. Finally, at bar 131, there is the last fugal entry in the lowest manual part. After each of these fugal entries, episodes are freely developed over brief pedal points. In bars 132–134, the rising quaver scales in the pedals lead up to the final section. •
Bars 135–151. There is a pedal point for four bars, with the upper manual parts accompanying the arpeggio motifs in the lowest manual part; that is followed by solo arpeggio pedalwork for seven bars; then, in a virtuosic cadenza-like coda, the regular semidemiquaver passage-work in the highest part leads up to an emphatic closing cadence in the minor key. The fugue is in
time, unlike the prelude, which is in
time. The fugue theme, like that of the prelude, is composed of
arpeggiated chords and downward sequences, especially in its later half. Due to the sequential nature of the subject, the majority of the fugue is composed of sequences or cadences. The Fugue ends in one of Bach's most
toccata-like, virtuosic cadenzas in the
harmonic minor. Unlike most of Bach's minor-key keyboard works, it ends on a minor chord rather than a
picardy third. == Reception and arrangements ==