It is, however, an exceedingly remarkable fact that, although among insects and lower vertebrates the sexual influence of music is so large, and although among mammals and predominantly in man the emotional and æsthetic influence of music is so great, yet neither in man nor any of the higher mammals has music been found to exert a predominant sexual influence, or even in most cases any influence at all. Darwin, while calling attention to the fact that the males of most species of mammals use their vocal powers chiefly, and sometimes exclusively, during the breeding-season, adds that "it is a surprising fact that we have not as yet any good evidence that these organs are used by male mammals to charm the female."[114] From a very different standpoint, Féré, in studying the pathology of the human sexual instinct in the light of a very full knowledge of the available evidence, states that he knows of no detailed observations showing the existence of any morbid sexual perversions based on the sense of hearing, either in reference to the human voice or to instrumental music.[115]
When, however, we consider that not only in the animals most nearly related to man, but in man himself, the larynx and the voice undergo a marked sexual differentiation at puberty, it is difficult not to believe that this change has an influence on sexual selection and sexual psychology. At puberty there is a slight hyperæmia of the larynx, accompanied by rapid development alike of the larynx itself and of the vocal cords, which become larger and thicker, while there is an associated change in the voice, which deepens. All these changes are very slight in girls, but very pronounced in boys, whose voices are said to "break" and then become lower by at least an octave. The feminine larynx at puberty only increases in the proportion of 5 to 7, but the masculine larynx in the proportion of 5 to 10. The direct dependence of this change on the general sexual development is shown not merely by its occurrence at puberty, but by the fact that in eunuchs in whom the testicles have been removed before puberty the voice retains its childlike qualities.[116]
As a matter of fact, I believe that we may attach a considerable degree of importance to the voice and to music generally as a method of sexual appeal. On this point I agree with Moll, who remarks that "the sense of hearing here plays a considerable part, and the stimulation received through the ears is much larger than is usually believed."[117] I am not, however, inclined to think that this influence is considerable in its action on men, although Mantegazza remarks, doubtless with a certain truth, that "some women's voices cannot be heard with impunity." It is true that the ancients deprecated the sexual or at all events the effeminating influence of some kinds of music, but they seem to have regarded it as sedative rather than stimulating; the kind of music they approved of as martial and stimulating was the kind most likely to have sexual effects in predisposed persons.