Guidonian Hand (late 15th century) Magnet

Guidonian hand from a manuscript from Mantua, last quarter of 15th century. 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 c. 1105–1110 did describe Guido using the joints of the hand to aid in teaching his hexachord.