Born in the last decade of the 10^th century, Guido d’Arezzo was a monk and music teacher at the Benedictine Abbey of Pomposa. However, he left following the refusal of his community to accept his pedagogical innovations: he is credited with developing a new method of teaching music that aimed beyond the oral tradition and direct imitation of a teacher.

Fortunately, he was welcomed to the Cathedral of Arezzo by Bishop Theodald (1023-1036), who was in favour of his innovations in teaching liturgical singing. On certain issues, such as the measurement of musical intervals, Guido saw well ahead of the common knowledge of his time: he tried to extend the use of lines, adding also different colours, to create a stave because, as he said, “a piece written in neumes without lines is like a well that lacks a rope to reach the water” (Regulae Rythmicae).

On top of the usage of lines to indicate the heights of pitches, of which he is not the inventor but which was his main topic of focus, Guido added a technical process which would have consequences far beyond the mere pedagogical field. He is said to have given a name to each of the notes of the hexachord, inspired by the hymn to John the Baptist attributed to John the Deacon (Johannes Hymonides): UT queant laxis REsonare fibris MIra gestorum FAmuli tuorum, SOLve polluti LAbii reatum, Sancte Ioannes (ut, ré, mi , fa, sol, la). The musical scale thus acquired a concrete means of expression, giving singers a practical and direct nomenclature for differentiating and ordering the notes used. .

According to his letter Epistola de ignoto cantu (‘Letter about an unknown song’), Guido was invited to Rome to demonstrate to Pope John XIX (1024-1033) the benefits of his solfeggio (solfège) method, with his antiphonary written according to his new technique of a four-line stave. Guido managed to get the Pope to sing a verse he had never heard before. Guido’s codification thus marked a turning point in the history of Western music.