The clavichord produces sound when metal tangents strike its strings.
A clavichord key is connected directly to a small metal blade called a tangent. When the key is pressed, the tangent contacts the string and both strikes it and determines the sounding length. This direct mechanism allows subtle control of pitch and expression.
Clavichords were used in Europe from the late Middle Ages through the eighteenth century, especially for domestic practice and intimate performance. They are quiet, which limited their usefulness in large rooms.
The piano also uses hammers, but its hammers rebound from the strings, while clavichord tangents remain in contact as long as the key is held. A harpsichord plucks strings with a plectrum instead of striking them.