e made a beginning in
canonic imitation, Coussemaker and Naumann, after him, giving examples
from a composition of his called "_Posuit Adjutorium_." In these works
of Perotin, and in many others of that day, traces are to be seen of
an amelioration of the musical ear, and a preference for thirds and
sixths, such as but a short time previously had been unknown to
musical theory. This influence was probably due to what was called
"_Faux Bourdon_," a system of accompanying a melody by an
extemporaneous second and third part in thirds or sixths.

This art, again, is clearly due to the influence of the round singing
of the British isles. Thus we have already a beginning of at least
three important elements of good music: The recognition of the triad,
or, more properly, of the third and sixth, a beginning in imitation,
and the contrapuntal concept of an independently moving melodic
accompaniment to a second voice, which in turn had been the outcome of
extemporaneous descant. The works of Perotin were undoubtedly in
advance of his time, having in them no small vitality, as is shown in
their having formed a part of the repertory of Notre Dame for more
than two centuries.

The second period of the old French school extended from about 1140 to
1170, and great improvements were made in the art of harmony
meanwhile. The three great masters of this period were Robert of
Sabillon, his successor in Notre Dame, Pierre de la Croix, and a
theoretical writer named Jean de Garland. The first of these men was
distinguished as a great deschanteur, in other words, a ready hand at
extemporaneous counterpoint. Pierre de la Croix made certain
improvements in notation, the nature of which, however, the musical
historians fail to give us. Garland divided the consonances into
perfect, imperfect and middle--a system which has remained in use,
with slight alteration, to the present day. The thirds and sixths,
however, still rank as dissonances. He also defines double
counterpoint, and gives examples. The illustrations are crude, but the
idea is correct.

The third period of the old French school is sometimes known as the
Franconian period, from the two great names in it of Franco of Paris
and Franco of Cologne, whose theories have already been noticed. (See
page 146.)

Another celebrated name of this period was that of Jerome of Moravia,
also a theoretical writer, whose treatise has been published along
with the others in Coussemaker's "Mediaev