Czech Chamber Music Society • Mahan Esfahani

Until the 18th century, musicians and audiences were accustomed to being limited to just a few keys with key signatures having up to three sharps or three flats, and all repertoire was written, played, and listened to in those tonalities. The other keys served only for brief “excursions” with the special effect of increased tension and emotional power. The chords in those remote keys sounded more or less unpleasant and out of tune. Musicians relied on various complex systems of tuning based on the mathematical relationships between all the intervals lying within each (always pure) octave. Some of the intervals sounded pleasant, while others had false intonation, and composers used the clashing intervals deliberately to express intensity and shifts of emotion. One of the most widely used tuning methods was the meantone temperament based on pure thirds (major and minor), but at the expense of other intervals, which grated on the ears. In all tuning methods (such as Werckmeister or Kirnberger, named for their inventors), composers worked with the “colours” of the individual keys and their corresponding shades of emotional expression. Some keys were clear and radiant, while others were dark and full of tension. And some could not be used at all. Therefore, besides tempo and dynamics, the music of the Baroque had another scale for shadings, and the composers, performers, and audiences of the time were well versed in this mode of expression.

Even during the period of the High Baroque, there was not yet any great need to spread the intervallic “clashes” evenly among all twelve notes of the octave. The system now known as “equal temperament” had already been invented in theory in the 17th century in China, and it was known to Europe as well, but the musical world did not begin using it until the 19th century with the arrival of a new kind of music and the need for the reliable use of all keys. Johann Sebastian Bach employed an intermediate stage known as “well-tempered tuning” for something of an experiment. In 1722 he wrote a systematically ordered series of compositions for keyboard instrument (harpsichord at the time), with a pairing of a prelude and a fugue in each key. He did not state the exact system for tuning the harpsichord, and there is speculation whether the temperament was to have been that of Werckmeister or Kirnberger (Kirnberger had been Bach’s pupil). The idea was for all the compositions to be played without retuning, so that every key had its own character, but without any key being unusably out of tune. Today, Bach’s Well-Tempered Clavier is routinely played using a piano with equal temperament, but the use of a harpsichord and a carefully chosen temperament is more appropriate for an authentic Bach sound.

In those days, it was a daring idea to propose that a keyboard instrument could sound relatively “in tune” in all 24 major and minor keys and that one could pass from one to another without unpleasant intonation problems. Bach wrote his cycle in Köthen, where he was employed by Leopold, Prince of Anhalt-Köthen. That was his only engagement as a Kapellmeister for instrumental music. Everywhere else, his responsibility had been overseeing church music in positions that involved daily duties. During his six years in Köthen, he enjoyed greater creative freedom, resulting in works like the Brandenburg Concertos, the sonatas and partitas for solo violin, or the suites for solo cello. And then there was the Well-Tempered Clavier.

The title page of the autograph manuscript bears the following text in Bach’s hand: “The Well-Tempered Clavier, or Preludes and Fugues going through all diatonic and chromatic keys both major and minor, composed and prepared for the benefit and use of the musically eager youth, as well as for the entertainment of those already established in this study, by Johann Sebastian Bach, Kapellmeister in Köthen, 1722.” Bach wished to draw attention to the collection’s practical, even didactic purpose to demonstrate the possibilities of equal temperament and to make innovative use of the full spectrum of tonalities. The result is an encyclopaedia of styles and affects arising from the characteristics of the different keys. The cycle contains 24 preludes and 24 fugues arranged in pairs ascending the chromatic scale: C major, c minor, C sharp major, C sharp minor, D major, D minor etc. until reaching B major and B minor. Ascending by semitones, Bach chose the enharmonically equivalent key signature with sharps or flats that was more convenient. 

Because the same two musical forms (a prelude and a fugue) constantly alternate, the 24 examples give us a fine introduction to the character of those genres. The preludes are entirely free compositions without a strict rhythmic or melodic structure and are based on virtuosic runs and unrestrained brilliance. Such an introduction is followed by a fugue, the supreme expression of contrapuntal thought. The preludes are deliberately diverse. Some of them make the impression of a stylised improvisation, such as the opening C major prelude with its broken chords, borrowed in the 19th century by Gounod as the accompaniment to his Ave Maria. By contrast, some are more like dance movements or rhythmic etudes, while others are reminiscent of Baroque toccatas or showy French overtures. Bach uses their harmonic layouts to explore how the colour of the instrument changes when modulating to harsher-sounding keys with more sharps or flats. The fugues represent order, but with Bach, order is lively and dramatic. The basic building blocks of the clearly given form are the subject, the response in the key of the dominant, the countersubject, the exposition, episodes, and finally variation techniques like inversion, augmentation, or stretto, with overlapping entrances of the theme and rising tension. In Book I of The Well-Tempered Clavier, we find mostly three-voice fugues, rare cases of fugues for two voices, and a few more for four voices. In them, Bach systematically explores how far he can go in terms of the density of texture without losing transparency. We also find him working with affects (C minor), elements of the dance (G major), and even the pathos of the liturgical sound of the organ (E flat minor).

For listeners who might be worried about a static structure with constant repetition, The Well-Tempered Clavier has a clear answer: the opposite is the case. The cycle has a clear internal rhythm, as each paring of a prelude with a fugue creates a natural contrast: improvisatory freedom versus disciplined order, sonic texture versus linear voice leading, spontaneous inventiveness versus long-term structural tension. Supplementing this bipolarity is a “promenade” through the varied colourings of the different keys: from the brilliance of C major to the hushed quality of E minor, or from flowing with ease in G major to pondering the depths of B minor. In 1722, Bach proved that tempered tuning, whether using various kinds of “well-tempered” approaches of his day or the later equal temperament, opens up a whole spectrum of possibilities to musicians. What would seem to be mere mathematics and craftsmanship are put at the service of imagination and expression. When the final B minor chord dies away, we have the peculiar impression that we have circled the globe while having never once stepped away from the instrument, and that we have discovered something both timeless and fantastical, embodying both order and freedom.

Thanks to the many copies soon made by Bach’s pupils and his wife Anna Magdalena, the collection quickly spread all over Europe. In the 1780s, Beethoven’s teacher Christian Gottlob Neefe wrote that his young pupil was “mastering” the preludes and fugues of The Well-Tempered Clavier; all his life, Beethoven returned to Bach, and he is widely quoted as having called this cycle the “daily bread” of a true pianist. Chopin was also said to have enjoyed starting his day with a prelude and fugue, and his own 24 preludes, Op. 28, bear a striking structural resemblance to Bach’s series.

Nearly 20 years after Part I, Bach composed another series of 24 preludes and fugues—Book II of The Well-Tempered Clavier—in Leipzig in the early 1740s in reaction to the great acclaim the first cycle had received. We will be hearing more about that later this season on 6 April 2026.