A friend sent me an interesting link to Wikipedia https://en.wikipedia.org/wiki/Guidonian_hand on the Guidonian Hand. Used in Medieval music, the Guidonian hand was a mnemonic device used to assist singers in learning to sight-sing. From Wikipedia: "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." Most of us have heard of the idea of tying a string around a finger to help us to remember something we might forget. The Guidonian Hand suggests the potential for our hands ...