FIG. 8-4 Phillippe de Vitry, Tuba sacre/In arboris/VIRGO SUM (Ivrea, Biblioteca Capitolare, MS 115, fols. 15 v–16). The tenor
notes that appear gray are notated in red ink to show a hemiola (3:2) proportion.
As for the tenor, its rhythms are cast in no simple modal ordo, but in an arbitrary arrangement of
values adding up to 24 breves, as follows (a number in italics indicates a rest): 4 2 2 2 2 3 2 1 2 4 . Note
the odd number in the middle. The composer might have indicated that one perfect long within a
prevailing duple modus by simply dotting it—as we still do, even if we do not know that we are
following the method introduced by the Ars Nova for converting imperfect values into perfect ones.
Another way of indicating the perfect long would have been by applying to it an explicit mensuration sign.
The way that Vitry actually did it was playfully ostentatious. He supplied the tenor with a supplementary
performance direction—called a rubric (after the red ink in which such things were often entered) or a
canon, meaning “rule”—that reads, Nigre notule sunt imperfecte et rube sunt perfecte (“The little black
notes are imperfect and the red ones are perfect”). Like so many of Philippe de Vitry’s innovations, this
one became standard practice. As a later theorist wrote, “red notes are placed in motets for three reasons,
that is, when they are to be sung in some other mode, or other tempus, or other prolation than the black
notes, as appears in many motets composed by Philippe.”^7
EX. 8-3 Philippe de Vitry, Tuba sacre/In Arboris/VIRGO SUM