Guido of Arezzo (also Guido Aretinus, Guido da Arezzo, Guido Monaco, or Guido d'Arezzo) (991/992 – (17 May?) 1050) was 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, was the second-most-widely distributed treatise on music in the Middle Ages (after the writings of Boethius).
Guido was a monk of the Benedictine order from the Italian city-state of Arezzo. Recent research has dated his Micrologus to 1025 or 1026; since Guido stated in a letter that he was thirty-four when he wrote it, his birthdate is presumed to be around 991 or 992. His early career was spent at the monastery of Pomposa, on the Adriatic coast near Ferrara. While there, he noted the difficulty that singers had in remembering Gregorian chants.
He came up with a method for teaching the singers to learn chants in a short time, and quickly became famous throughout north Italy. However, he attracted the hostility of the other monks at the abbey, prompting him to move to Arezzo, a town which had no abbey, but which did have a large group of cathedral singers, whose training Bishop Tedald invited him to conduct.
While at Arezzo, he developed new techniques for teaching, such as staff notation and the use of the "ut–re–mi–fa–so–la" (do–re–mi-fa-so-la) mnemonic (solmization). The ut–re–mi-fa-so-la syllables are taken from the initial syllables of each of the first six half-lines of the first stanza of the hymn Ut queant laxis, whose text is attributed to the Italian monk and scholar Paulus Diaconus (though the musical line either shares a common ancestor with the earlier setting of Horace's "Ode to Phyllis" (Odes 4.11) recorded in the Montpellier manuscript H425, or may even have been taken from it.)
Guido is credited with the invention of the Guidonian hand, a widely used mnemonic system where note names are mapped to parts of the human hand. However, only a rudimentary form of the Guidonian hand is actually described by Guido, and the fully elaborated system of natural, hard, and soft hexachords cannot be securely attributed to him. The Micrologus, written at the cathedral at Arezzo and dedicated to Tedald, contains Guido's teaching method as it had developed by that time. Soon it had attracted the attention of Pope John XIX, who invited Guido to Rome. Most likely he went there in 1028, but he soon returned to Arezzo, due to his poor health. It was then that he announced in a letter to Michael of Pomposa ("Epistola de ignoto cantu") his discovery of the "ut–re–mi" musical mnemonic. Little is known of him after this time.
The computer music notation system GUIDO music notation is named after him and his invention.
The International International Guido d'Arezzo Polyphonic Contest (Concorso Polifónico Guido d'Arezzo) is named after him. - Arezzo, Province of Arezzo, Italy