TONES IN SIMULTANEOUS COMBINATION: HARMONY
WHEN TWO OR MORE TONES of the scale are sounded simultaneously they make either a consonance or a dissonance. A succession of consonances and dissonances is in itself not harmony, since such a succession does not, as such, constitute a harmonic progression. But a simultaneous tonal combination is, nevertheless, the unit of harmony, as the single tone is the unit of melody. Just, then, as there are laws that operate in melodic tonal successions, so there are laws that function in the making of a series of consonances and dissonances into a harmonic sequence. Our concern here, however, is not with the laws of harmonic progression, but with the phenomenon of consonance itself. What is the nature of the experience of consonance? What accounts for the phenomenon? How do the different intervals of the scale rank in consonance? These are some of the psychological questions that have been investigated, and it is this literature we are to survey.
The most prominent theory of consonance is that of fusion, but the criterion for fusion is not the same for different investigators.
Stumpf (107), who was among the first to examine consonance psychologically, defines fusion as the experiencing of two elements as one. Two simultaneous tones give the impression of a single tone in different degrees, and the greater the impression of singleness of the two tones the greater is the consonance of the interval. But that does not mean that the two tones are heard as one tone. Fusion is a relation of two such sensations forming not a mere sum but a whole. He holds that