Chiroplast

A chiroplast is an instrument to guide the hands and fingers of pupils in playing on the piano, invented and patented by Johann Bernhard Logier in 1814. The instrument was an device that placed the wrist, thumb and fingers of a hand above five consecutive white keys of a keyboard, to overcome the difficulty of retaining their proper position by beginners.

Description
The device consisted of a wooden framework screwed into place over the whole length of the keyboard. The user passed their wrists through two parallel wooden bars, which kept the wrists at the right level, and put their fingers into slots in two flat brass frames called "finger-guides" which could freely slide along a brass rod along the whole length of the keyboard. Each finger-guide had five divisions, through which each finger was placed. Each finger-guide was also attached to a stiff brass wire with a regulating screw, which kept the wrist in the proper position relative to the arm. It was patented on 28 April 1814, patent no. 3806 "Apparatus for facilitating the acquirement of proper execution on the piano forte". The use of the chiroplast caused a significant amount of criticism and controversy, at least part of which was due to the heavy opposition at the time to Logier's system for teaching multiple students at once, in which the chiroplast was a key part.