The Well-Tempered Clavier is two sets of preludes and
fugues for keyboard. Each set consists of twenty four
preludes and fugues in all of the major and minor keys
in ascending order. They were published in two separate
"books," Book I, which was composed in 1722, and Book
II, composed in 1744. The title of the work refers to a
then new system of tuning, called equal temperament, in
which an octave was divided into twelve equal
intervals. This method of tuning replaced an earlier
one called meantone tuning, in which the key of C major
and those near it were purely intonated, while keys
with many sharps or flats would be out of tune. In the
meantone system, each tone and semitone is subtly
different, while the equal tempered system eschewed
perfect intonation for an equal division of the octave,
such that each tone and semitone was equal. Bach
certainly recognized the value of such a system--it
allowed for greater freedom of modulation and use of
chromaticism--and his Well-Tempered Clavier served as
an effective promotion of this new tuning method. It is
a vivid demonstration of the flexibility and
practicality of the equal or "well" tempered keyboard.
It is also an example of Bach's compositional genius
and good taste: as his first biographer Johann Forkel
noted, despite its perfectly idiomatic music and
attention to specific technical issues, Bach likely
composed this work away from the keyboard while on a
trip with his patron, Prince Leopold.
Like many of Bach's great pedagogical works, the
Well-Tempered Clavier is a collection of pieces whose
musical value is as great as their instructional value.
Each piece tests different techniques and addresses
different technical challenges; however, Bach is
careful not to sacrifice musicality for pedagogy, so
that fugal subjects are simple yet interesting, motives
are tastefully developed, and melodic lines are supple
and shapely. There is no paucity of purely musical
ideas in this work. Book II, composed some twenty-two
years after the first, is noticeably less pedagogical
in its emphasis, and is obviously addressed to the
accomplished player rather than the "Musical youth"
described on the title page of Book I. Book II also
does not, in the printed score, make a point of equal
temperament: by 1744, this new system was no longer
new, and no longer required Bach's advocacy.
One might expect this prelude and fugue that follow
those in A flat major to be in A flat minor; Bach,
however, prefers to label the key G sharp minor --
essentially the same thing, although the ears of Bach's
time, accustomed to the vagaries of other tuning
systems, would have anticipated a slight difference in
character between the two. The prelude flows and rolls
smoothly through a three-voice texture; the fugue
employs a somewhat menacing, or at least mysterious,
theme quite contrasting with the good-natured prelude.
Structurally it's a straightforward piece in four
voices, the subject arriving first in the tenor, then
alto, soprano, and bass.
Although originally written for Harpsichord. I created
this Arrangement of the Fugue in G# Minor (BWV 863 No.
2) for String Quartet (2 Violins, Viola & Cello).