Guidonian hand
In Medieval music, the Guidonian hand was a mnemonic device used to assist singers in learning to sight-sing. Some form of the device may have been used by Guido of Arezzo, a medieval music theorist who wrote a number of treatises, including one instructing singers in sightreading. The hand occurs in some manuscripts before Guido's time as a tool to find the semitone; it does not have the depicted form until the 12th century. Sigebertus Gemblacensis in 1105–10 did describe Guido using the joints of the hand to aid in teaching his hexachord. The Guidonian hand is closely linked with Guido's new ideas about how to learn music, including the use of hexachords, and the first known Western use of solfege.
Michelangelo Hand
The Michelangelo Hand is a fully articulated robotic hand prosthesis developed by the German prosthetics company Ottobock and its American partner Advanced Arm Dynamics. It is the first prosthesis to feature an electronically actuated thumb which mimics natural human hand movements. The Michelangelo Hand can be used for a variety of delicate everyday tasks, was first fitted to an Austrian elective-amputee in July 2010 and has been in use by military and civilian amputees in the United States and United Kingdom since 2011.