In addition to all other demands upon his time - church organist, cantata composer, civil servant, and (most irksome of all) Latin tutor to mischievous choir boys - Johann Sebastian Bach (1685-1750) also taught numerous pupils within his family orbit. Bach always needed small-scale works with which to demonstrate principles of composition. Several volumes collated these pieces, including two from the early 1720s. Bach had recently remarried after his first wife’s death, and the Notebooks for Anna Magdalena Bach contain dozens of pieces written out by his new bride. Another important collection, a Notebook for Wilhelm Friedemann, includes music Bach used when teaching his young sons. These simple works, crystalline in their structural clarity, show the patterned harmonic progression and general shape that would become central to more expansive preludes in The Well-Tempered Clavier, completed in 1722.

By nature, a prelude serves several functions, one of which is to allow a performer to improvise or “warm up” within a particular key. It may lead into a more structured series of contrapuntal episodes or a set of tonally-related dances. To his preludes, Bach usually joined a fugue in the same key. Like partners in a dance, prelude and fugue pairings express themselves best when in each other’s company. A prelude sets the key in our ears and delights by virtue of various textures, melodic turns of phrase, and harmonic color. The fugue then imposes a certain order on affairs; it is architecturally sound yet aesthetically moving, guiding our minds through a series of contrapuntal twists and turns.

Building on examples from his predecessors, Bach decided to produce a set of preludes and fugues in all 24 possible keys. Before the 18th century, not every key was usable due to inconsistencies in different tuning systems. Unequal systems or temperaments allowed the most common keys to sound wonderfully in tune, but outlier tonalities (for instance, F-sharp major or B-flat minor) contained harsh, discordant intervals that rendered them off limits. Thus earlier collections tended to be smaller series of organ Magnificats, for instance, demonstrating only the eight church keys or modes. Even Bach’s own two-voice Inventions and three-voice Sinfonias use only 15 keys, staying within the limited range of four sharps and flats (i.e., E major and F minor).

Bach’s expansion to all 24 major and minor keys in Das Wohltemperierte Clavier represents a significant milestone. And the title directly comments on that fact. As mentioned above - and skirting the edges of a complex topic - older tuning systems sought purity of certain commonly-used intervals at the expense of entire swaths of other pitches. Eventually, most of Western Europe would adopt equal temperament: a system that divides the musical octave into 12 equal steps, thereby ensuring access to all keys uniformly. The term wohltemperierte or “well-tempered” proceeds in that direction but does not call for exact consistency. Instead, it provides a compromise. Not all keys and intervals are mathematically equal, yet enough adjustments are made to allow the musician to explore in each of the 24 keys.

It may suffice, then, to say that Bach’s Well-Tempered Clavier served a demonstrable and pedagogical function. Having spectacularly achieved that purpose in the first book of the WTC (1722), what need for a second complete collection of preludes and fugues twenty years later? Most casual admirers of Bach’s keyboard works get no further than WTC 1. Appreciation for WTC 2 seems more rare, the collection itself a bit more esoteric, a realm perhaps for connoisseurs. The composer himself did not prepare a handwritten fair copy, evidence that he viewed it somewhat less formally or “publicly” than WTC 1. By the early 1740s Bach was nearing the end of his life. He could afford to entertain valedictory projects that would memorialize his abiding interest in polyphony (i.e., The Art of Fugue and The Musical Offering). It is also possible that Bach felt a renewed interest in keyboard composition due to the new fortepianos reaching the market. For various reasons, therefore, he still had much to say in the Prelude and Fugue genre from a purely creative standpoint.

From the widest perspective, both collections present pairs of tonally-unified preludes and fugues. And yet, like the twinning resemblance between parent and child, there are important differences that mark WTC 2 as better suited to its time. Let’s begin with the preludes. First, the “pattern preludes” familiar from the 1722 collection are largely missing by the time Bach put pen to paper in the 1740s. Several WTC 2 preludes even last longer than their companion fugues. Second, counterpoint plays a significant role in so many preludes that it becomes the dominant aesthetic experience of the entire collection, even beyond the nominal fugues. Numerous preludes (c, d, d#, e, G, a, and others) feature invertible counterpoint in the manner of the two-part Inventions; one Prelude (C#) even includes a Fughetta within its bounds. Further, somewhat hidden within the generic Prelude designation are many binary-form dances, including the Allemande (c, D, d#, E, a), Corrente (e), Bourrée (f), and Gigue (F, Bb). Others touch on specific musical topics, such as French Overture (F# and g), Pastorale (A), March (e), and the Toccata (d, G, g#, B). This astounding diversity of style, form, and topic helps enliven music that, in lesser hands, could become stale and repetitive.

Regarding the companion fugues, a similar wealth of invention carries technical complexity into the realm of aesthetic enjoyment. In WTC 1 Bach flirted with extreme examples of two- and even five-voiced fugues; by 1744 the field has been leveled out to include only examples in three and four voices. The most common fugue types feature a subject in “instrumental style,” creating polyphonic displays of vigor and motoric intensity (C, f, f#, G, g, A, a, bb, b). Some of these (d, f#, Ab, g#, a, bb) are also bolstered by a high degree of chromaticism, further intensifying the listening experience. Still, Bach also found space for fugues marked by deep introspection - and usually a slower tempo (c, g#) - as well as some inspired by his study of older vocal music (Eb, E, B). As in the preludes, we encounter dances among the fugues, including a Gigue (c#), Bourrée (f), Gavotte (F#), Minuet (Bb), and Passepied (b). Finally, on some occasions Bach found that a single fugue subject was inadequate to capture his prodigious ambitions. Four examples (f#, g#, Bb, B) offer double or triple fugues, often closing with a statement of all themes at the same time.

Such intricate counterpoint was generally rejected by the generation of Bach’s sons and students, and his music fell out of fashion for many years. Yet the WTC volumes retained an important place on composers’ desks. Mozart and Beethoven both admired the grandly synthetic scale of Bach’s effort; the former transcribed several WTC fugues for string quartet, and Beethoven’s early command of the entire WTC helped fuel his prodigious reputation. Composer-pianists from Chopin and Schumann to Shostakovich made their debt of homage clear to all. What these masters found in Bach’s keyboard music is still there for us to discover - maybe rediscover - today.

(c) Jason Stell, 2026