Guido of Arezzo (also Guido Aretinus, Guido da Arezzo, Guido Monaco, or Guido d'Arezzo, or Guy of Arezzo) (991/992 – after 1033) is a music theorist of the Medieval era.
He is regarded as the inventor of modern musical notation (staff notation) that replaced neumatic notation; his text, the Micrologus, is the second-most-widely distributed treatise on music in the Middle Ages (after the writings of Boethius).
