um" already given, upon the sweetness of which Hucbald greatly
prided himself.

Fetis has well said that Hucbald must be considered as one of those
superior spirits who impress upon their epoch a movement in an art or
science. Besides this, he merits particular mention in the history of
music because his works are the first since those of Boethius--a
period of four centuries--in which the art of music is treated
systematically and without obscurity.

In the "_Epistola de Harmonica Institutione ad Rathbodum Episcopum
Trevinesem_" ("Letter to Rathbodum, Bishop of Treves"), there is
mention of the instruments of music during the seventh and eighth
centuries. They are the cithara and harp as the stringed instruments;
musetts, syrinx and organ among the wind instruments; cymbals and
drums, instruments of percussion. In the tenth century there was a
methodical treatise upon music in dialogue form, published by Odon,
abbot of Cluny, who died in this monastery November 18, 942. This
work, which was wrongfully attributed to Guido of Arezzo, contains a
number of analyses of intervals showing an understanding of the exact
dimensions of the various kinds of fourths, fifths, thirds and sixths.
According to his doctrine, the intervals of the fourths, fifths and
octaves are more natural for the voice than the others called thirds
and sixths, because the former are invariable, while the latter may be
larger or smaller by a half step. He makes a summary of ecclesiastical
chant, mentioning the modes as established by St. Gregory,
illustrating each of them by a selection from the "Plain Song." It is
a fact significant of the unsettled condition of musical theory and
the complete unconsciousness of musical amateurs that any essential
change in the art was being undergone, that as late as 1000 or 1020
Adelbold, Bishop of Utrecht, published a treatise upon music in which
the proportions of the tetrachords are calculated carefully according
to the Greek theories, and demonstrated upon the monochord.

III.

The most important writer upon music in the eleventh century, and one
of the most famous in the history of the art, was a monk named Guido,
living at Arezzo, in Tuscany, a Benedictine in the abbey of Pontose.
He was a remarkably skillful teacher of ecclesiastical singing, both
in his own monastery and at Rome, and in the effort to systematize the
elements of music he introduced a number of important reforms, and is
credited by later