See P. James, Early Keyboard Instruments (1930); D. Matthews, ed., Keyboard Music (1972).
It was very popular from the 16th century to the 18th century, but mainly flourished in German-speaking lands, Scandinavia, and the Iberian Peninsula in the latter part of this period. It had fallen out of use by 1850. In the late 1890s, Arnold Dolmetsch revived clavichord construction and Violet Gordon-Woodhouse, among others, helped to popularize the instrument. Although most of the instruments built before the 1730s were small (four octaves, four feet long), the latest instruments were built up to seven feet long with a six octave range.
Today clavichords are played primarily by Renaissance, Baroque, and Classical music enthusiasts. They attract many interested buyers, and are manufactured worldwide. A modern clavichord can range in price from $2,400 to as much as $20,000. There are now numerous clavichord societies around the world, and some 400 recordings of the instrument have been made in the past 70 years. Leading modern exponents of the instrument include Derek Adlam, Christopher Hogwood, Richard Troeger, and Miklos Spányi, and fine modern instruments are widely available. Some modern makers include Peter Bavington and Karin Richter in Great Britain, Joris Potvlieghe in Belgium, Thomas Steiner in Austria, and Ronald Haas, Owen Daly, Charles Wolff, David Jensen, and Andrew Lagerquist in the United States.
Tori Amos also uses the instrument on "Little Amsterdam" from the album Boys For Pele as well as on the song "Smokey Joe" from her 2007 album American Doll Posse. And in 1976 Oscar Peterson played (with Joe Pass on acoustic guitar) songs from Porgy And Bess on the clavichord. Keith Jarrett also recorded an album entitled "Book of Ways" (1987) in which he plays a series of clavichord improvisations. The Beatles' "For No One" (1966) features Paul McCartney playing the clavichord to tremendous effect.
The action of the clavichord is unique among all keyboard instruments in that one part of the action simultaneously initiates the sound vibration while at the same time defining the endpoint of the vibrating string, and thus its pitch. Because of this intimate contact between the player's hand and the production of sound, the clavichord has been referred to as the most intimate of instruments. Despite its many (serious) limitations, including extremely low volume, it has considerable expressive power, the player being able to control attack, duration, volume, and even provide certain subtle effects of swelling of tone and a type of vibrato unique to the clavichord.
Since the string vibrates from the bridge only as far as the tangent, multiple keys with multiple tangents can be assigned to the same string. This is called fretting. Early clavichords frequently had many notes played on each string, even going so far as the keyed monochord — an instrument with only one string — though most clavichords were triple- or double-fretted. Since only one note can be played at a time on each string, the fretting pattern is generally chosen so that notes which are rarely heard together (such as C and C#) share a string pair. The advantages to this system compared with unfretted instruments (see below) include relative ease of tuning (with around half as many strings to keep in tune), greater volume (though still not really enough for use in chamber music), and a clearer, more direct sound. Among the disadvantages: temperament could not be re-set without bending the tangents; and playing required a further refinement of touch, since notes sharing a single string played in quick succession needed to be slightly separated to avoid a disagreeable deadening of the sound, potentially disturbing a legato line.
Some clavichords have been built with a single pair of strings for each note. The first known reference to one was by Johann Speth in 1693 and the earliest such extant signed and dated clavichord was built in 1716 by Johann Michael Heinitz. Such instruments are referred to as unfretted whereas instruments using the same strings for several notes are called fretted. Among the advantages to unfretted instruments are flexibility in tuning (the temperament can be easily altered) and the ability to play any music exactly as written without concern for "bad" notes. Disadvantages include a smaller volume, even though many or most unfretted instruments tend to be significantly larger than fretted instruments; and many more strings to keep in tune. Unfretted instruments tend to have a sweeter, less incisive tone due to the greater load on the bridge resulting from the greater number of strings, though the large, late (early 19th century) Swedish clavichords tend to be the loudest of any of the historic clavichords.
While clavichords were typically single manual instruments, they could be stacked to provide multiple keyboards. With the addition of a pedal clavichord, which included a pedal keyboard for the lower notes, a clavichord could be used to practice organist repertoire. In the era of pipe organs which used hand-pumped blowers, and of churches which were only heated during church services, organists used pedal harpsichords and pedal clavichords as practice instruments (see also: pedal piano). There is speculation that some works written for organ may have been intended for pedal clavichord. An interesting case is made by Joel Speerstra that Bach's "Eight Little Preludes and Fugues", now thought to be spurious, may actually be authentic. The keyboard writing seems unsuited to organ, but Speerstra argues that they are idiomatic on the pedal clavichord.