The clavinet (or Clavichord) is a stringed instrument operated by a keyboard, and enclosed in a rectangular box. Clavinet seems to be an alternative name for the clavichord. 

This is an old European instrument dating from the 1500s, and it was eclipsed by the invention of the piano in around 1770. It has a very soft tone, easily drowned out by other instruments. But it allowed the performer to achieve louder or softer sounds by striking the keys with varying degree of force. Playing a key causes a brass blade called a tangent to press against the string. Early clavichords had a range of only 3 octaves, later ones had 4.