The irregular air-vibrations arising from the disturbances in the tonal waves, excite both the nervous elements in the vestibule of the labyrinth, which are sensitive to such stimulations, and the auditory nerve fibres themselves. It is assumed that certain parts of the auditory organ are so tuned that tonal waves of a given rate always set in sympathetic vibration only the part ,correspondingly tuned. This explains in a general way the analyzing ability of the auditory sense, as a result of which we can distinguish the elements not only in a compound clang, but to some extent even in a single clang. The resonance hypothesis, however, accounts physiologically for only one side of tonal fusion. The tonal elements that produce an intensive clang-idea persist as real sensations and still give up their independence more or less in the total idea.
Tonal fusion is, then, a psychical process and requires a psychological explanation.
The most natural way to attempt such an explanation is properly to supplement the resonance hypothesis. If we assume that besides the analysing parts of the auditory organ, the resonant membrane, still others exist which are effected by the total, unresolved clang, we have a sufficient physiological substratum for the different effects of the various conditions. The single clangs of such a series arrange themselves in the same phases as these overtones, and the compound clang has the character of a single clang with very strong overtones. But as the idea of a single clang can not be produced in this way, it is probable that an entirely constant relation of the phases of different tonal vibrations from independent sources can never be brought about with this method.