relative. There is no such thing as a dissonant tone in music, by
itself considered; a tone becomes dissonant by being brought into
juxtaposition with some other tone with which it does not agree. This
part of the development of a tonal sense had its beginnings in Greece,
but only reached the point where the most elementary relations were
regarded as agreeable. The octave, the fourth and the fifth, were the
only consonances which they knew, and of these they used in the
combined sounds of their music only the octave. The third, which with
us is the most agreeable part of a pure harmony, because it adds so
many elements of agreement to the combined sound into which it enters,
was not only regarded as a dissonance by them, but actually _was_ a
dissonance as they tuned their scale.

The entire course of harmonic perception in modern music may be
roughly divided into three steps: First, the recognition of
consonance, especially of the most fruitful consonance of all--that of
the thirds, and the differentiation between consonance and dissonance.
A second step involved the recognition of dissonance as an element in
musical expression, on account of the motion it imparts to a harmonic
movement. Third, the establishment of these materials of music in the
mind in such depth and fullness that their aesthetic implications
became realized as elements of expression, so that when a composer had
a certain feeling to express, the proper combination of consonance and
dissonance immediately presented itself to his mind. The first of
these steps was taken by the minstrels of the north, somewhere between
the Christian era and the tenth century. The second was the particular
work of the old French school, the Netherlanders, and of all who
composed music between about 1100 A.D. and the epoch of Palestrina,
about 1600. The third, the spontaneous application of musical material
to the expression of feeling, had in it another element, that of
tonality, concerning which it is proper to say something at this
point.

By "tonality" is meant the dependence or interdependence of all the
tones in a key upon some one principal tone called the Key-tone. The
tonality of the music of the ancients was wholly artificial and
unreal. A mode and a point of repose for the melody were chosen
arbitrarily; the beginning was here made, and still more the ending
was conducted to this point of repose. Between the beginning and the
ending the same tones were employe