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.^[1][2] The instrument was a 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.^[1]

The instrument was a key part of Logier's system of teaching, which was one of the first to call for the teaching of multiple students at once.^[3] The use of the chiroplast caused a significant amount of criticism and controversy at the time,^[1] at least part of which was due to the heavy opposition to Logier's system by musicians fearing the loss of their students to centralized institutions teaching multiple students at once.^[2]

After being invented by Logier in 1814, it quickly became used by many.^[4] It was very popular in London in the 1810s and 1820s.^[5] In 1822, Logier was invited by the Prussian government to Germany to set up a school instructing teachers on how to teach the use of the device in the country.^[4]

The device consisted of a wooden framework screwed into place over the whole length of the keyboard.^[2] The user passed their wrists through two parallel wooden bars,^[2] which kept the hands at the correct distance from the keys.^[5] They then put their fingers into slots in two flat brass frames called "finger-guides" which could freely slide horizontally along a brass rod along the whole length of the keyboard.^[2] Each finger-guide had five divisions, through which each finger was placed.^[6] 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.^{[6][clarification needed]}