The first book of J. S. Bach's Das Wohltemperierte
Klavier (The Well-Tempered Clavier) was complete by
1722. Bach gave the present title to the work, which
was composed "for the use and practice of musical youth
eager to learn and for the amusement of those already
skilled in this study." Bach composed a paired Prelude
and Fugue in each of the 24 keys to demonstrate the
viability of the new "equal-temperament" system, which
allows one to play in all keys without producing
out-of-tune intervals, ...(+)
The first book of J. S. Bach's Das Wohltemperierte
Klavier (The Well-Tempered Clavier) was complete by
1722. Bach gave the present title to the work, which
was composed "for the use and practice of musical youth
eager to learn and for the amusement of those already
skilled in this study." Bach composed a paired Prelude
and Fugue in each of the 24 keys to demonstrate the
viability of the new "equal-temperament" system, which
allows one to play in all keys without producing
out-of-tune intervals, as happened with Pythagorean and
"mean tone" tunings. Furthermore, the pieces are as
much compositional studies as keyboard works.
Twenty years later, Bach assembled another set of
preludes and fugues. The title page is missing from the
manuscript, but its similarity to the "first" book of
The Well-Tempered Clavier led editors to entitle it
"Book II." Bach worked on the second book over a long
period of time, even reworking pieces he had written
for other purposes, as he had in the first book. Some
of the preludes and fugues date from the 1720s.
Possibly the most substantial revision for the second
book was to No. 3, in C sharp major, which was
originally in C major. Fugues Nos. 15 and 17 survive in
earlier versions in which they are connected with
different preludes than we find in The Well-Tempered
Clavier.
There are many musical differences between the works of
Book II and those of Book I. The preludes in the second
group explore a greater range of forms and styles than
do the earlier examples. Most striking are the
experiments in the style of the Italian bipartite
keyboard sonata, codified by Domenico Scarlatti. Like
earlier dance movements, these consist of two repeated
sections. Some of the "sonata" preludes in Book II,
such as Nos. 5, 12, and 21, feature a recapitulation of
the opening material, while others (Nos. 10 and 15)
have parallel closing sections. Prelude No. 17 is an
Italian concert-ritornello movement; Nos. 13 and 23
also display concerto traits. The tenth is a two-part
invention and Nos. 4 and 14 are ariosos. Those that are
clearly derived form dance forms -- No. 5 from the
gigue and No. 8 from the allemande -- lack the
traditional binary form.
The prelude, with its chromatically falling primary
theme, is a two-part invention exploring its melodic
intricacies at some length before finally giving way to
the short fugue. This latter item, inspired by the
French toccata pathétique, begins with a hesitant,
rest-dotted subject that looks forward to the basis of
Bach's Art of the Fugue. Here, the three voices enter
in ascending order, with the faster notes of the
countersubject soon providing contrast.
SHEET MUSIC