Over the next two weekends Yuliya Gorenman will be performing the entire Book I of the Well-Tempered Klavier by Johann Sebastian Bach, half on the June 22nd program and half on the June 28th program. Most classical music aficionados have heard of this particular collection of Bach’s compositions, and it contains some of his most famous and frequently-performed works. But what is it that makes this specific set of Preludes and Fugues so interesting?

Bach was, first and foremost, a keyboardist. Most of his compositions were for keyboard, or included the keyboard in some way. His instrument of choice was the organ, though he also played on the harpsichord and clavichord. At the time, each of these instruments was tuned so that the intervals of a single key sounded right. This meant that an instrument tuned to play in C Major sounded most in tune in that key. Closely related keys like G Major and F Major sounded almost in tune, but distant keys like F# Major and Ab Major sounded so terribly out of tune that they could not be played.

The idea of tuning a keyboard so it could be played in all keys had been around for almost 100 years by the time Bach was born, but nobody had yet discovered how to achieve an equal-temperament tuning in a way that could be reasonably replicated from instrument to instrument. Dietrich Buxtehude had been working on the equal-temperament theory for some time when a young Bach came to visit him, and Bach took the idea home, much to dismay of his employers and congregation as he attempted to play in the more dissonant keys on an organ with a single-key temperament.

Around this same time the pianoforte was invented in Italy, with a relatively equal temperament. It could be used to play in each of the 12 Major and 12 minor keys, though some still sounded slightly better than others, and the instrument was prone to going out of tune quickly. However, Bach would not have regular access to a pianoforte for some time, and instead adapted the equal-temperament tuning structure to tune his harpsichord to be able to play in all 24 keys. It was on this uniquely-tuned harpsichord that Book I of the Well-Tempered Klavier was written, as an exploration of a single keyboard’s ability to play in each of the 24 known keys.

Even more than a masterful exploration of equal temperament and Bach’s mastery of the Prelude and Fugue forms, however, the Well-Tempered Klavier was a snapshot of folk, church, and court music at the time. Bach used melodies and themes from a variety of sources as his inspiration, particularly for his Fugues. Though the form remains constant, each of the Preludes and Fugues has its own unique character, a tribute to both Bach’s mathematical precision and his artistry as a composer.

Yuliya Gorenman will be performing all 24 Preludes and Fugues from Book I of the Well-Tempered Klavier over the next two weeks. The first 12 will be performed at the June 22nd Evening Concert, with the second 12 opening the June 28th Evening Concert. Tickets are available at the door, at Old Harbor Books in downtown Sitka, or online.