FRANCO OF COLOGNE. – Music theorist and composer, active in the 13th century (ca. 1250–80). Manuscripts of his works indicate that he was chapel master to the Pope and instructor at the Hospital of St John of Jerusalem in Cologne (C. Coussemaker, *L'art harmonique au moyen âge*, Paris 1865, p. 22).
Of his activity as a composer there is mention by Jacques de Liège, who, in Book VII of the *Speculum musicae*, states that he heard in Paris a *triplum* (a three-voice composition) attributed to F. of C. (C. Coussemaker, *Scriptores*, II, p. 402).
As a theorist he gave his name to a new period in the history and notation of music, inasmuch as he codified pre-existing rules and added others concerning the division of the *brevis* into three *semibreves*, ligatures, consonances and dissonances, etc., in the *Compendium discantus magistri Franconis* (op. cit., I, pp. 134–36) and especially in the *Ars cantus mensurabilis* (M. Gerbert, *Scriptores*, III, pp. 1–16; C. Coussemaker, op. cit., I, pp. 117–36). This latter treatise was formerly attributed to Franco of Paris, an ill-defined figure perhaps slightly earlier, to whom a passage in the anonymous IV of Coussemaker (op. cit., I, p. 342) refers when speaking of two Francos. The theoretical work of Franco of Paris may be connected with a commentary and three compendia, all beginning in the same way, evidently derived from the original (n. *Coudent revivitate moderni*), published by C. Coussemaker himself (op. cit., I, pp. 202–96, 303–19, 319–27, 383–403). The Franco system, used in its broad outlines until the end of the 16th century, underpins modern mensural notation.
The principal manuscripts of the Franco treatises are found in Paris (Bibliothèque Nationale), Oxford (Bodleian Library), London (British Museum), Milan (Biblioteca Ambrosiana), etc.