181. Harmony is the science of chord construction and combination.
The term harmony refers to tones sounding simultaneously, i.e., to chords, as differentiated from tones sounding consecutively, as in melody. The word harmony may therefore be applied to any group of tones of different pitches sounded as a chord, although specifically we usually refer to a succession of such chords when we speak of "harmony." It is possible to use the same combination of tones in either melody or harmony; in fact these two elements as applied to modern music have developed together and the style of present-day melody is directly based upon the development that has recently taken place in harmonic construction.
Harmony (as contrasted with counterpoint) first began to be an important factor in music about 1600 A.D., i.e., at the time when opera and oratorio came into existence, when form was established, and when our modern major and minor scales were adopted. Before this practically all music was composed on a contrapuntal basis.
182. Timbre is that peculiar quality of sound which enables one to distinguish a tone produced by one instrument (or voice) from a tone produced by an equal number of vibrations on another instrument.
The word timbre is synonymous with the terms quality of tone, and tone quality (Ger.—Klang-farbe), the excuse for using it being that it expresses adequately in one word an idea that in our language takes at least two: this excuse would disappear (and incidentally a much-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.
184. In classifying intervals two facts should be constantly kept in mind: