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.
Guidonian hand
The hexachord as a mnemonic device was first described by Guido of Arezzo, in his "Epistola de ignoto cantu" and the treatise titled "Micrologus". It was the most basic pedagogical tool for learning new music in the European Middle Ages, and was often referenced in contemporary musical theory. In each hexachord, all adjacent pitches are a whole tone apart, except for the middle two, which are separated by a semitone. These six pitches are named "ut", "re", "mi", "fa", "sol", and "la", with the semitone between "mi" and "fa". These six names are derived from the first syllable of each half-line of the 8th century hymn "Ut queant laxis".