ed led to an
entirely different kind of singing, called _falso bordone_
or _faux bourdon_ (_bordonizare_, "to drone," comes from a
kind of pedal in organum that first brought the third into
use). This system, contrary to the old organum, consisted of
using only thirds and sixths together, excluding the fourth
and fifth entirely, except in the first and last bars. This
innovation has been ascribed to the Flemish singers attached
to the Papal Choir (about 1377), when Pope Gregory XI returned
from Avignon to Rome. In the British Museum, however, there
are manuscripts dating from the previous century, showing
that the _faux bourdon_ had already commenced to make its way
against the old systems of Hucbald and Guido. The combination
of the _faux bourdon_ and the remnant of the organum gives us
the foundation for our modern tone system. The old rules,
making plagal motion of the different voices preferable to
parallel motion, and contrary motion preferable to either,
still hold good in our works on theory; so also in regard to
the rules forbidding consecutive fifths and octaves, leaving
the question of the fourth in doubt.

To sum up, we may say, therefore, that up to the sixteenth
century, all music was composed of the slender material of
thirds, sixths, fifths, and octaves, fourths being permitted
only _between_ the voices; consecutive successions of fourths,
however, were permitted, a license not allowed in the use of
fifths or octaves. This leads us directly to a consideration
of the laws of counterpoint and fugue, laws that have remained
practically unchanged up to the present, with the one difference
that, instead of being restricted to the meagre material of
the so-called consonants, the growing use of what were once
called dissonant chords, such as the dominant seventh, ninth,
diminished seventh, and latterly the so-called altered chords,
has brought new riches to the art.

Instead of going at once into a consideration of the laws
of counterpoint, it will be well to take up the development
of the instrumental resources of the time. There were three
distinct types of music: the ecclesiastical type (which of
course predominated) found its expression in melodies sung
by church choirs, four or more melodies being sometimes sung
simultaneously, in accordance with certain fixed rules,
as I have already explained. These melodies or chants
were often accompanied by the organ, of which we will speak
later. The second typ