counterpart to verse. In this form it evidently went from mouth to mouth for a generation or two before a
notation for it was invented. And when the notation for it was invented, it was not really for it, but for
something else. Again, and even more spectacularly, what was prompted by practical need became the
stimulus for luxuriant artistic play.
Here is where the generation of Anonymus IV’s “Perotin the Great” comes in. As you may recall, the
treatise credits the great discantor with having abbreviavit the Magnus Liber. The translation has been put
off until now because the word has an ambiguous range of meaning in Latin. The closest English cognate,
“abbreviated,” though followed by many writers, does not seem to fit the facts of the case, since so many
“substitute clausulas” (like the one on “Do-” in Ex. 6-3c) so clearly lengthen rather than shorten the
pieces into which they are inserted.
Another possible translation of abbreviavit is “edited.” This fits better, since the differing versions of
the organum duplum repertory in the four Notre Dame sources obviously show the hand of a reviser—or
likelier, of many revisers. And yet, to cite a case we have already seen, the presence of the same revised
“Do-” clausula within the body of the organum in W 2 and in the section containing the “substitute
clausulas” in Flo would seem to indicate that whoever revised the Magnus Liber did not have in mind the
goals of a modern editor. That is, he (or they) aimed not at establishing an improved, corrected, or
definitive text. The aim, rather, seems to have been just to make a wealth of interchangeable material
available.
And so we are left with the third and most general possible translation of abbreviavit—simply,
“written down.” This one not only fits but explains a great deal. If we assume that the “Perotin”
generation finally wrote down the music of the “Leonin” generation (in the process devising a notational
method that opened up a whole new world of musical possibilities that they were quick to exploit), then
we can not only account for the gap between the twelfth-century repertory and its thirteenth-century
sources, but also make sense of the fact that the theoretical descriptions of modal rhythm come as late as
they do. As a fully elaborated system of metrics and notation, modal rhythm pertains not to the orally
created and rhythmically transmitted music of the Leonin generation, but to the very intricate and stylized
output of the Perotin generation, which is found in all its many sources in essentially one version, and
which may have been the first musical style in the West that actually depended on notation for its
composition.
ORGANUM CUM ALIO
The major works of the Perotin generation differ from those of the previous generation in one fundamental
respect. They are written for more than two parts—or, to make the point in most essential terms, they are
written for more than one part against the Gregorian tenor. That is why contemporary theorists called their
style organum cum alio (“organum with another [voice]”) to distinguish it from organum per se
(“organum by itself”).
The presence of the added voice or voices changed everything. They moved at the rate of the duplum,
not the tenor (so they were called the triplum and, when present, the quadruplum). Two or three parts
moving at a similar rate are in effect in discant with one another, regardless of whether there is a long-
held tenor note, and so they had to be notated throughout in strict modal rhythm (modus rectus, as it was
called). Everything now had to move in countable perfections; there could be no spontaneous
coordination in performance, the way there could be with a single cantor in the driver’s seat, ad-libbing
“freely” and giving all necessary signals to his subordinates on the tenor line.
For an example of organum cum alio at its most luxuriant, we can examine the fourpart setting