Clavichord -the lonely, melancholy, inexpressibly sweet instrument

Principle: The clavichord has the simplest action of all keyboard instruments. The metal "tangent",sitting at the far end of the key lever; hits the string and remains there as long as the keylever is depressed. If the depth of key depression is varied, the tone makes a nice vibrato known as "Bebung" (literally, trembling). Touch and articulation are very sensitive and expressive.
The clavichord sound typically has a rich overtone spectrum and a rather low volume level. Together with the vibrato and the touch sensitivity, this creates a very expressive, intensive and soulful instrument.
During the second half of the 18th century, a period known as the "Empfindsamkeit", many composers considered the clavichord the ideal expressive instrument for their music. This was particularly true of both Wilhelm Friedemann and Carl Philipp Emanuel Bach.
The clavichord has a long tradition throughout Europe, starting in the 14th century. It reached its peak in Germany, Spain and Sweden in the 17th and 18th centuries, when it was held in particularly high esteem. All important composers and keyboard players of the time were masters of the clavichord, including Froberger, Pachelbel and Mozart. It was Johann Sebastian Bach's favorite instrument.
The growing importance of the Pianoforte early in the 19th century, and the increasing emphasis on loudness, led to the clavichord's fall from favor, after which it served just as a composing instrument (for Beethoven, Bruckner and Brahms, among others) until the middle of the 19th century.
The current renaisssance of early music has led to the clavichord's rediscovery. A growing number of music lovers are attracted to the qualities of this interesting instrument. Additionally, clavichords, which are usually quite small, can satisfy the desire of many buyers for an affordable hand-crafted instrument.

"The clavichord, this lonely, melancholy, inexpressibly sweet instrument,
has, when made by a master, superior qualities to a harpsichord or fortepiano.
... For the feeling player, a more perfect instrument does not exist."

(C.F.D. Schubart: "Ideas Towards an Esthetic of the Musical Art", 1785)