d the germs of the most important devices
of counterpoint.

Leonin was known to his contemporaries as "Optimus Organista," on
account of his superior organ playing. He wrote a treatise upon the
art, a manuscript copy of which appears to be in the British Museum,
and its contents have been summarized by an anonymous observer, but
never published in full. He is said to dwell mainly upon the proper
manner of performing the antiphonary and the graduale. It is also
stated that he noted his compositions according to a method invented
by himself. If this work could be fully examined it might throw
important light upon the point reached in the practice of church music
in his day; his notation, also, would be a matter of interest and
possibly of importance. Quite a number of compositions by Leonin have
been discovered. The successor of Master Leonin, as director of the
music at Notre Dame, was one Perotin, who, besides being a capable
deschanteur, was an even greater organist than his teacher, Leonin. He
was also a very prolific composer, many of his compositions being
still extant. He made additions to his predecessor's manual of the
organ.

By descant in the foregoing account, reference is made to the practice
of extemporaneous singing of an ornamental part to the plain song or a
secular _cantus fermus_. This art had its origin one or two centuries
earlier than the period now under consideration, in the secular
organum of Hucbald (see p. 142), and all the more talented singers,
who were also composers as well, were expert masters of it. Descant
was the predecessor of counterpoint.

The chief forms of composition in vogue during this period were
motette, rondo and conduit. The terms were rather inexactly applied,
but in general the motette appears to have been a church composition,
in which often the different voices had different texts, so that the
words were wholly lost in performance. The rondo seems to have been a
secular composition, and was sometimes written without words. The
conduit was an organ piece, occasionally, if not generally, of a
secular character. All of these forms were also distinguished as
duplum, triplum and quadruplum, according to the number of voices. The
harmonic treatment in them is still crude, occasional passages of
parallel fifths occurring, after the manner of Hucbald, but in the
works of Perotin passages of this kind are softened somewhat by the
device of contrary motion in the other parts. H