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“Every keyboardist should own a good harpsichord and a good clavichord to enable him to play all things interchangeably. A good clavichordist makes an accomplished harpsichordist, but not so the reverse. The clavichord is needed for the study of good performance, and the harpsichord to develop proper finger strength.” With these words from his 1753 Versuch über die wahre Art, das Clavier zu spielen, Carl Philipp Emanuel Bach joined his father, Johann Sebastian, in his praise of the clavichord as a keyboard instrument suitable for performing, teaching, composing and practicing.

The action of the clavichord is unique among all keyboard instruments in that the  depression of a keyed lever causes a wedge-shaped “tangent” to rise and strike a metal string in order to set it into motion as well as define its length and, therefore, pitch. Because of this intimate connection between the player’s fingers and the vibrating string, the clavichordist is able to control attack, duration, and even a type of vibrato, unique to the clavichord, called Bebung. The instrument’s expressiveness, however, is limited by its extremely low sound power output, and, as a result, clavichord performances are mostly limited to small rooms.

The earliest clavichords were “fretted” in that a single string could be used to create more than one pitch, depending on where along its length it was struck by a tangent. Unfretted clavichords with a single note per string, however, appeared by the late seventeenth century. They allowed their players to more readily adjust the size of each interval and thereby establish a temperament that might enable performances in all keys and, eventually, modulation into distant keys. Instruments with such capabilities probably inspired Johann Sebastian Bach’s The Well-Tempered Clavier Books I and II (BWV 846-69 and BWV 870-93), published in 1722 and 1742, but no records describing Bach’s instruments or their builders’ identities have survived.

Much of the solo repertoire written between 1400 and 1800 for organ, harpsichord and fortepiano can be played on various forms of the clavichord, but, with the possible exception of providing very light accompaniment to a Baroque traverse flute, recorder, or single singer, the clavichord is an unsuitable partner in chamber music.

Christopher Hogwood performs Partite diverse sopra il Corale “O Gott, du frommer Gott” (BWV 767) on a clavichord recording, entitled The Secret Bach, released on the Metronome label. The liner notes for that compact disc include an essay by Derek Adlam, historic instrument builder and restorer, performer, and President of the British Clavichord Society.