Boris Giltburg: Well-Tempered Clavier I

Although many of us are familiar with the title The Well-Tempered Clavier, Book I, it does bear some unpacking to understand all the elements that are reflected in its name.

The word tempered refers to a tuning system. The tuning system that we use now is called equal temperament, which means that the distance between every half step is exactly equal. But in tuning an instrument using the perfect intervals that exist in nature, you will come to the end of the entire scale and find that there are chords that sound in tune and chords that sound out of tune. This system, which is often referred to as mean-tone tuning, caused real problems for composers who wanted to compose in every key. Those tuning systems, or temperaments, went through considerable revisions during Bach’s lifetime. Ultimately, a system was devised that allowed a composer like Bach to compose in every key, white note and black note, with all of the keys sounding relatively in tune, even though it fell short of the equal temperament that we use today. So in the title, “well-tempered” means that he is using such an evened-out tuning system.

The word Clavier in German simply refers to a keyboard, although even this presents some questions. What keyboard instrument is Bach indicating? Certainly the harpsichord, but also very possibly the clavichord, a smaller and more intimate household instrument that Bach seems to have liked. With a clavichord, a small piece of metal not only hits the string but maintains contact with it, allowing the player to continue to manipulate the sound, even using a little bit of vibrato with their finger.

But we also shouldn’t rule out the organ. I have heard performances of this collection of pieces by a keyboard player who shifted between clavichord, piano, harpsichord, and organ—all very effectively. We can rule out the piano in Bach’s case; yes, he did encounter the new instrument at the court of Frederick the Great near the end of his life, but there is no evidence whatsoever that he had the new fortepiano in mind when he composed. But as you will hear tonight—and as you may certainly have heard in outstanding recordings over the years—the piano is perfectly suited to the wide range of emotions and musical styles in the WTC.

And “Book I”? Well, Bach wrote two of these Well-Tempered Clavier collections. The one that you will hear this evening dates from early in his years in Leipzig, in the early 1720s. However, some of the movements are found in the Notebook for Wilhelm Friedemann Bach (his eldest son) from the prior decade. This indicates that at least to some extent Bach thought of these works as pedagogical, just as the Inventions had been. But not just pedagogical for players: Bach was always very careful to compose collections like this in such a way that his sons and students could learn all of the various compositional techniques and devices at their disposal.

And all of that is just a definition of the title! As for the works themselves, this universe of musical expression requires a concert, not a set of program notes. How lucky we are to hear this entire book of preludes and fugues—there, we have two more words to define—in one sitting. This feat is an impressive one for any pianist, and it also requires a great deal of concentration from the audience. But that concentration is well rewarded.

As its name suggests, a prelude is a piece that precedes another one. There isn’t much of a definition beyond that; a prelude can take so many different forms, from a majestic French overture to one of the several French dance forms. I like to think of the preludes in WTC Book I as almost improvisational. Listen carefully to the first few measures in each prelude: Bach will often build an entire piece around the melodic, harmonic, and rhythmic motives that he establishes from the outset. Like so much of Bach’s music, the preludes are fundamentally generative—he creates and unfolds an organic movement from the seed of the opening idea.

For audiences of THE COMPLETE BACH, a fugue needs a little introduction. It is a fancy kind of round or canon, with the opening subject returning throughout the fugue as a melodic point of reference. A fugue is fundamentally contrapuntal, meaning that Bach weaves independent lines around one another to create a sonic tapestry. The second most important material is the countersubject, composed quite literally to complement the subject. Personally, I love the challenge of following the subject as it moves from register to register in the piano, called voices even on a keyboard instrument. There will be sections, known as episodes, where the fugue subject is not present, only to re-enter at various junctures, sneaking in like a lamb or roaring in like a lion.

There is a major-key prelude and fugue pair and a minor-key pair for each note on the keyboard from C to B. Not every note name is represented; for example, there is no pair in either D-sharp major or D-sharp minor, since Bach chooses the enharmonic equivalent of E-flat instead. But if you follow in your mind’s eye a keyboard with its alternating white keys and black keys, you can keep track of the 24 pairs as we go along.

– Chris Shepard

BACHtoberfest Spotlight: Boris Giltburg
Jenny Pacillo, The Pulse (October 22, 2026)