Guido of Arezzo was an 11th-century Benedictine monk and Italian music theorist. During his time at the abbey, he realized singers needed a faster, easier way to memorize the chants that so often saturated the hallowed air.

Guido crafted a system that used lines, clef signs, and colors to indicate the pitch, which transformed music into information that could be read and stored in a book rather than solely tucked away in one’s mind. As the inventor of modern staff notation, he became a musical revolutionary.