Proposes a common prototype from the tradition of illustrated manuscripts of Cassiodorus’s Institutiones as the explanation for the close iconographic relationship between music illustrations in a manuscript (here dated to the 11th century) of the De arithmetica and De musica of Boethius (Milan, Biblioteca Ambrosiana, MS C.128 inf.) and in the 12th-century Codice Magno (Piacenza, Biblioteca Capitolare, MS 65). Suggests that the iconography may have originated in a Carolingian scriptorium.