ch-mispronounced word
would be eliminated) if the single word _quality_ were to be
adopted as the equivalent of _timbre_. Thus, _e.g._, the
soprano voice singing c' has a _quality_ different from the
contralto voice singing the same tone.

(The remainder of this chapter and all of Chapter XVIII deal
with terms commonly encountered in the study of _harmony_.
Courses in this subject usually begin with a study of scales,
but since this subject has already been somewhat extensively
treated, this chapter will omit it, and will begin with the
next topic in harmony study, viz.--the interval.)

183. An _interval_ is the relation of two tones with regard to pitch. If
the two tones are sounded simultaneously the result is an _harmonic
interval_, but if sounded consecutively the result is a _melodic
interval_. Fig. 62 represents the pitches f' and a' as a harmonic
interval, while Fig. 63 represents the same pitches arranged as a
melodic interval.

[Illustration: Fig. 62.]

[Illustration: Fig. 63.]

184. In classifying intervals two facts should be constantly kept in
mind:

(1) The _number name_ of the interval (third, fifth, sixth,
etc.), is derived from the order of letters as found in the
diatonic scale. Thus the interval C--E is a _third_ because E
is the third tone from C (counting C as one) in the diatonic
scale. C--G is a _fifth_ because G is the fifth tone above C
in the diatonic scale.

It should be noted however that the same _number-names_ apply
even though one or both letters of the interval are qualified
by sharps, flats, etc. Thus _e.g._, C--G[sharp] is still a
_fifth_, as are also C[sharp]--G[flat] and C[flat]--G[sharp].

(2) In determining the _specific_ name of any interval
(_perfect_ fifth, _major_ third, etc.), the half-step and
whole-step (often referred to respectively as _minor second_,
and _major second_) are used as units of measurement.

The _half-step_ is usually defined as "the smallest usable
interval between two tones." Thus, C--C[sharp] is a
_half-step_, as are also B--C, F--G[flat], etc.

A _whole-step_ consists of two half-steps. C--D is a
_whole-step_, as are also B[flat]--C, E--F[sharp],
F[sharp]--G[sharp], G[flat]--A[flat], etc.

The expressions _half-step_ and _whole-step_ are much to be
preferred to _half-tone_ and _whole-