What is "clavicytherium"

A clavicytherium is a harpsichord in which the soundboard and strings are mounted vertically facing the player. The primary purpose of making a harpsichord vertical is the same as in the later upright piano, namely to save floor space. In a clavicytherium, the jacks move horizontally without the assistance of gravity, so that clavicytherium actions are more complex than those of other harpsichords.