Before the Renaissance, artists (like composers and songwriters) were artisans and did not sign their work, similar to illustrators and jingle-composers today. The "Master of St. Cecilia" decorated churches in Assisi and in Florence from around 1300-1320.
This fresco is from his Legends of St. Francis, #27 (A heretic confessing) in the Upper Church, San Francesco, Assisi (1300)