Guido of Arezzo was an 11th century Italian music theorist who is considered the inventor of modern musical notation. He replaced neumatic notation with staff notation, using lines and spaces to indicate pitch. His text "Micrologus" was the second most widely distributed treatise on music in the Middle Ages. Guido created the pentagram, designing a new concept for musical notation that uses a five-line staff. His system of musical notation using the staff is still used as the basis for music composition today.