Franco of Cologne (active ca. 1250-1260), or Franco of Paris, was the outstanding music theorist of his century.
Thirteenth-century Paris was a cultural and political center that attracted numerous foreign artists and scholars. It was there that for longer or shorter periods of time men from many countries taught during the midcentury at the great new university: the German St. Albertus Magnus, the teacher of St. Thomas Aquinas and an outstanding philosopher, who in 1248 retired to Cologne; St. Thomas himself and his Italian compatriot St. Bonaventura; the English humanist John of Garland; and others. One of these scholars was Franco of Cologne, who received the honorary title of papal chaplain and became the preceptor, that is, head, of the Cologne branch house of the Order of St. John, probably in the early 1260s. These positions indicate that he was of noble birth, but no more is known of him.
Franco's fame derives from his treatise Ars cantus mensurabilis (The Art of Measurable Music), written about 1260. This treatise is preserved in seven manuscripts dating from the 13th to the 15th century and written in France, England, Sweden, and Italy. Numerous quotations from it and references to it appear in the literature of several countries, and its great influence on composition between 1250 and 1320 can be detected in many works. None of Franco's own compositions can be identified. Some motets are briefly quoted or cited in treatises; only one motet, in a German manuscript of the 13th century, has been tentatively ascribed to him.
Franco's treatise presents a new concept of musical notation, on which several other theorists were working at the time, about 1240-1270, but Franco gives the clearest and most logical exposition, and thus he had the widest and longest-lasting influence among all the authors of his period. He was the first to teach distinct note symbols for several clearly related note values, namely, the so-called longa, brevis, and semibrevis, the last of which developed into the modern whole note. Only with the help of this notation did it become possible to write musical lines of much rhythmic variety.
In addition, Franco's teachings of consonances and dissonances and their uses became standard for a long time thereafter, and his approach to composition and analysis of the musical styles created by Léonin and Pérotin and their successors was adopted by the following generations. His importance was such that music historians at one time spoke of an "epoch of Franco."
Perhaps the best accounts of Franco's teachings are in Gustave Reese, Music in the Middle Ages (1940), and in Homer Ulrich and Paul A. Pisk, A History of Music and Musical Style (1963), although the dates given in the latter work must be revised.