Guido of Arezzo
11th century Italian monk, inventor of modern musical notation
Feast: 7 September (not on the universal Roman calendar; kept in the Roman Martyrology or local calendars)
Who they were
Guido, a Benedictine monk of St-Maur-des-Fossés near Paris, saw the confusion in the teaching of the Church's chant and worked to improve it, which made him unpopular with his brethren; he moved to Pomposa and then to Arezzo.
There he perfected the system of staff notation still used in music today. He is believed to have died as prior of a Camaldolese house near Avellano in 1050.
The miracles
The Catholic Encyclopedia does not describe how he came to be honoured as a saint.
Why that counted as sanctity
A monk who gave the Church and the world the musical staff.
- Catholic Encyclopedia (1913), via New Advent - Guido of Arezzo
- Wikidata Q192238 — dates, feast day and identifiers (CC0)
- English Wikipedia — Guido of Arezzo (CC BY-SA)
Checked against the sources listed on 21 September 2026. Corrections welcome.