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.
Guido Pisano
Either on 20 April (Easter), at Bamberg, or else on 23 April, at an imperial diet held in Nuremberg, he had a personal audience with Conrad. At the end of the month he met Wibald, a friend with whom he had corresponded by letters for over twenty years, in Würzburg. Guido joined Pope Eugene when the latter took ship from Pisa to France in 1147, there to hold several reforming councils and encourage the Second Crusade. Guido was with the Papal entourage when it entered Trier on 30 November. They returned to Rome in April 1148.