The precedent established by Jerome was followed and even expanded by Jacques de
Liège, a canon from Liège active in Paris during the early 14th century. Jacques’s
Speculum musice is the largest surviving medieval musical treatise, consisting of seven
books (521 chapters) treating every conceivable topic and drawing on virtually every
known source. The scholastic nature of the work is evident in the first book, where
Jacques draws not only on Boethius in setting the philosophical foundations of the study
of music, but on Aristotle, Robert Kilwardby, and Peter Comestor as well. After
systematically treating systems, consonances, melodic genres, division of the monochord,
solmization, and the modes, Jacques, in the seventh book, turned his attention to the
measured music of his time and railed against the musical practices of the 14th century.
The conservative Jacques, placing contemporary practices in sharp contrast to the
traditional mensural forms and practices of the 13th century, became an important early
witness for a historical consciousness within the tradition of music theory. The works of
Jerome and Jacques offer eloquent testimony to the wide variety of musical texts
available in Paris during the 13th and 14th centuries and to the influence of scholastic
culture’s demand for the universality of knowledge.
The contrast in style and content between the summae of Jerome of Moravia and
Jacques de Liège and the carefully wrought treatise of Johannes de Grocheio reflects the
stylistic shift in music itself between the Ars Antiqua and the Ars Nova. Johannes de
Grocheio explicitly rejected the quantitative, philosophical nature of past theoretical
reflections and attempted to develop a musical theory based on empirical observation
refined by rational organization. The basis of his work, now known by the title De
musica, was not ancient authority or even mathematical speculation but the musical life
that he experienced in Paris at the beginning of the 14th century. He divided music into
musica vulgaris, the everyday music of the city; musica mensurata, the composed music
of musician-scholars; and genus ecclesiasticum, the music of the church. His perceptive
descriptions of genres within these categories, sometimes offered with commentary on
poetic form and social function, transforms his iconoclastic discourse into an invaluable
historical record of contemporary musical life.
More representative of the French tradition of musical reflection are the works of two
early 14th-century magistri artium at the University of Paris, Jehan des Murs and
Philippe de Vitry. Both of these scholars were expert in the mathematical disciplines, and
their fame and reputation extended well beyond music and music theory. Jehan des
Murs’s Musica speculativa secundum Boetium seems to have functioned as a text in the
university curriculum, and his Opus quadripartitum numerorum, dedicated to Philippe de
Vitry, summarized the state of arithmetical knowledge. The Notitia artis musice
(formerly known as Ars nova musice), remains his most significant theoretical treatise.
Written ca. 1320, this work offers a clear, rational approach to the question of duple and
triple division of rhythmic values and extended the application of duple and triple
divisions to every level of rhythmic organization—maximodus, modus, tempus, and
prolatio. Shortly after Jehan des Murs’s work, Philippe de Vitry codified imperfect
(duple) mensuration, established the minim as the divisor of the semibreve, and even
opened the possibility of dividing the minim into semiminims. The practical clarity of
Philippe’s thought is most readily seen in his quatre prolacions, the four signs that
became universally recognized as the fundamental time signatures. The rational,
quantitative organization of time in the art of music offered by Jehan des Murs and
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