ear to certain melodic combinations (which
were originally hit upon by accident), and finally analyzing and
systematizing these combinations into a certain definite order or
arrangement. The application of this idea may be verified when it is
recalled that most primitive peoples have invented melodies of some
sort, but that only in modern times, and particularly since the
development of instrumental music, have these melodies been analyzed,
and the scale upon which they have been based, discovered, the inventors
of the melodies being themselves wholly ignorant of the existence of
such scales.

78. A _key_ is a number of tones grouping themselves naturally (both
melodically and harmonically) about a central tone--the key tone. The
word _tonality_ is often used synonymously with _key_ in this sense.

The difference between _key_ and _scale_ is therefore this,
that while both _key_ and _scale_ employ the same tone
material, by _key_ we mean the material in general, without
any particular order or arrangement in mind, while by _scale_
we mean the same tones, but now arranged into a regular
ascending or descending series. It should be noted in this
connection also that not all scales present an equally good
opportunity of having their tones used as a basis for tonality
or key-feeling: neither the chromatic nor the whole-step scale
possess the necessary characteristics for being used as
tonality scales in the same sense that our major and minor
scales are so used.

79. There are _three general classes of scales_ extant at the present
time, viz.: (1) Diatonic; (2) Chromatic; (3) Whole-tone.[13]

[Footnote 13: If strictly logical terminology is to be insisted upon the
whole-tone scale should be called the "whole-step" scale.]

80. The word _diatonic_ means "through the tones" (_i.e._, through the
tones of the key), and is applied to both major and minor scales of our
modern tonality system. In general a diatonic scale may be defined as
one which proceeds by half-steps and whole-steps. There is, however, one
exception to this principle, viz., in the progression six to seven in
the harmonic minor scale, which is of course a step-and-a-half. (See p.
33, Sec. 86.)

81. A _major diatonic scale_ is one in which the intervals between the
tones are arranged as follows:

1 whole 2 whole 3 half 4 whole 5 whole 6 whole 7 half 8
step step step