The clavichord is an early keyboard instrument of very simple construction, dating from the 14th century. It was primarily used in the home and by itself rather than in conjunction with other instruments. This is due to its diminutive tone and volume along with its limited tonal range. Many musicians regarded the clavichord to be well suited for practice and working out the melodies for larger compositions. There is an oft-told story of Handel, who was discouraged from following his musical passion by his father, sneaking a clavichord into his room at night in order to learn music secretly. The clavichord was perfectly suited for this sort of intimate use.
The clavichord consists of a shallow rectangular box with a keyboard encompassing 2-3 octaves. The strings run parallel to the keyboard from a hitch rail on the left side, over the back sides of the keys, across a curved bridge, and finally attaching to tuning pegs on the far right side. The soundboard is contained within the right side and is approximately one third the size of the instrument.
The clavichord is also regarded as one of the most intimate of keyboard instruments because of the control a musician has over the strings, much like a guitarist or violinist has. This is due to the way the instrument's action works, which is unique among all keyboard instruments. The string's vibrations are actuated in a deceptively simple fashion. The key is a simple lever, with a brass blade (or tangent) attached to the rear of the key. When the front of the key is pressed the rear end rises and the tangent strikes the string. However, unlike other keyboard instruments, the tangent remains on the string until the front of the key is released. This gives the musician control over the tension on the string, enabling various nuances such as the bebung effect (much like a violinist's vibrato).
In addition, unlike other keyboard actions, the key initiates the string vibration and acts as one of the termination points for the string, thus determining its pitch. With other keyboard instruments each key has its own string, which is of a set length and therefore a predetermined pitch. With the clavichord numerous keys use the same string, but strike it at different points, thereby varying the speaking length of the string and altering its pitch. So, each key plays a distinct pitch even though they use the same strings. This is what is known as a fretted clavichord. The principle is the same with a guitar or other stringed instrument - with a limited number of strings the musician varies the pitch by terminating the string length with a finger at different points along the fretboard. In the 17th century German makers developed an unfretted clavichord as well. These, of course, boasted a separate string for each key. Naturally, this made the instrument larger and broadened the range to 5-6 octaves.
During the 16th and 17th centuries clavichord use began to diminish as they were supplanted by two other smallish keyboard instruments: virginals and spinets. Clavichords did remain popular in Scandinavia and Germany, which remained the center of clavichord production. However, the instrument became virtually extinct by the early 19th century when it finally gave way to the preeminence of the piano. However, revived interest in the clavichord has been seen in recent years with numerous societies and builders popping up. Various musicians and scholars, such as Christopher Hogwood, have also helped revive the clavichord with their efforts to perform ancient music on authentic period instruments.