 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 Benedictine monk 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.