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 da Vigevano
Guido da Vigevano or Guido da Pavia (born c. 1280; died c. 1349) was an Italian physician and inventor. He is notable for his sketchbook "Texaurus regis Francie" which depicts a number of technological items and ingenious devices, allowing modern scholarship an invaluable insight into the state of medieval technology. Although still attached in style and spirit to the Middle Ages, Guido da Vigevano can be regarded as a distant forerunner of later Renaissance artist-engineers like Taccola, Francesco di Giorgio Martini and Leonardo da Vinci.