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.
Lodovico Grossi da Viadana
Viadana is important in the development of the early Baroque technique of basso continuo, and its notational method, known as figured bass. While he did not invent the method—figured basses occur in published sources from at least as early as 1597 —he was the first to use it in a widely distributed collection of sacred music ("Cento concerti con il basso continuo"), which he published in Venice in 1602. Agostino Agazzari in 1607 published a treatise describing how to interpret the new figured bass, though it is clear that many performers had by this time already learned the new method, at least in the most progressive musical centers in Italy.