=Principle of the Clavichord=.—The first of the Clavichord instruments had the name of Monochord, or one-stringed instrument—a name of great antiquity, first given by the Grecian Pythagoras to an instrument of one string used by him in determining the relations of tones. Similar experiments were made in the Middle Ages, in which the various tones resulting from the vibrations of parts of a string were studied by means of movable bridges; facility was gained by increasing the number of strings to four or five, tuned in unison. Next, _keys_ were applied to these in place of the bridges, which keys _struck the strings at various_ definite _points_ by means of upright pins or _tangents_, as they were called, producing varying pitches, according to the length of the part of the string allowed to sound, the remaining segment being silenced by a piece of cloth. Thus several tangents struck the same string at different points, producing different degrees of pitch. At first, when only the scales corresponding to the white keys were employed, four or five strings sufficed to sound the necessary tones, not over twenty-two in number. Later, however, when chromatic notes were adopted, the number of strings and keys was increased, so that, by the beginning of the 16th century, the keyboard had a range of three or four full octaves. From this time on, this instrument, now generally known as the Clavichord, won a popularity which extended to the beginning of the 19th century, when the Pianoforte gradually displaced it. A familiar instrument in England and Germany, it was especially cultivated by musicians of note in the latter country, even the renowned Bach preferring it to all other forms of its class. =The Clavichord=.—In shape, the Clavichord was an oblong box, the strings of brass extending lengthwise. The fact that one string served for several keys made it impossible to sound certain intervals together; yet the device of giving a separate string to each key seems not to have come in till about the year 1725, and even then not to have been generally adopted. Without legs, the Clavichord was supported on a table when in use. Its tone was exceedingly weak and tremulous, audible only within the distance of a few feet; yet the fact that this tone could be given different degrees of intensity, and could be varied to some extent even while sounding, by a peculiar pressure on the keys (_bebung_), imbued its tone with a sympathetic quality which helps to account for the tenacity with which musicians clung to it, notwithstanding all its imperfections. [Illustration: THE CLAVICHORD.]