Having thus considered how the glottis may act in the falsetto range, let us now examine in what way the vocal tube contributes to its formation. We have seen that this tube gra dually shortens during the ascent of the pri mary register, suddenly falls to its original length when the falsetto commences, and again diminishes during the secondary register. Now it appears from Savart's experiments that, notwithstanding the shortness of this tube, the wave length of a column of air vibrating within it is the same as that of a rigid pipe of much greater length, and we have therefore strong grounds for believing that the notes of the primary register are reinforced in con sequence of the vibrations of the glottis being always in unison with the fundamental pitch of the walls of the tube ; hence in the falsetto, when the vocal apparatus has resumed its original condition, there will be less reinforce ment of the sound, since the parietes of the vocal pipe are no longer in unison with the glottis, but give its grave octaves. We have found, by numerous experiments, that a flex ible disc will vibrate to almost any pitch, but will reinforce the sound in a trifling degree only, unless the pitch be in unison with its fundamental note ; and on the same principle we may suppose the intensity of the notes in the second register to be diminished, and their quality to be modified by the forced vibration of the walls of the tube, while in the primary all things concur in augmenting the effects produced by the glottis. Muller agrees with Lehfeldt.in opinion, that the falsetto notes are produced by the vibrations of the inner por tion of the borders of the vocal ligaments, and the variation of the pitch by their tension ; and, although he does not mention by what mechanism this is effected, he seems to attri bute it chiefly to the agency of the thyro arytenoid muscles. The author's explanation is in many points coincident with that of Milller, but he has taken into account one or' two circumstances which appear to have escaped Miiller's attention. The natural key or pitch of the vocal organs may be found by sounding the voice, without either elevating or depressing the larynx. The grave octave of that note will be the fundamental sound of the vocal ligaments vibrating in their nu st relaxed state, with the glottis entirely open. Any tones of a graver pitch, produced by an unusually relaxed state of the_vocal cords, lose both their quality and intensity, and cannot be included in the compass natural to the voice. According to the preceding principles, the pitch of the voice being usually an octave, or a fifth graver than the length of a column of air within the vocal pipe, we see the cause why a falsetto quality of sound cannot be obtained except during the production of acute tones. In many persons the speaking pitch is an entire octave graver than corresponds to the length of a tube, which would enable a column of air to produce the same sound ; and in such persons the falsetto can seldom be effected. In consequence of the pitch of the vocal organs thus occupying a middle or central position between the acute and grave notes, a great facility is afforded to their action in modulating the voice. The vocal tube, like any other tube open at both ends, is said to be capable of producing the harmonies of its fundamental tone in the ratio of the series of natural numbers, 1, 2, 3, 4. These harmonic sounds have been described by Knecht of Leipsic, and by Dr. Young. I have occasion ally thought that I have heard them during the forcible expiration which attends the bois terous laughter of children. The density of the air inspired is said to affect the pitch of the voice av in rigid tubes.
The influence of the epiglottis on the voice has been the subject of divers hypotheses. MM. Biot, Majendie, and Mayo have inferred, from the experiments of Grenie, that the epi glottis prevents the tones from becoming more acute when they increase in intensity. Lis covius, on the other hand, states that neither its depression, elevation, nor even its entire removal has any effect on the voice.* Haller
appears to have deduced the same opinion from the circumstance of birds being destitute of this organ. " Epiglottis equidem nihil facit ad vocem, cum ea (vox) nata sit et perfecta quamprimum aer ex glottidis rima prodit, et absque epiglottide ayes suavissime canant."1 According to Milder, the influence of this organ on the pitch of the voice is exercised during its depression only, rendering the tones graver, and at the same time duller. He thinks we evidently employ it in this H ay during the production of very deep tones ; and observes that, by introducing the finger at the side of the mouth, the epiglottis will be found to maintain the same position during the utter ance of musical notes, whether they be of the falsetto character, or of the ordinary scale. I am disposed to ascribe to the functions of the epiglottis much the same value as Mfiller ; since it is clear that its presence is not essen tial to the mere formation of voice, for it may be removed, together with the superior ligaments of the glottis, the ventricles of the larynx, and the cupitula laryngis of Santorini, without im peding the vibratory movements of the glottis.
The art of singing consists in the applica tion of the vocal organs to produce a certain succession of tones in some determinate order, which constitutes melody. This can be ac complished with precision by those only who can accurately discern with the ear, and imi tate with the voice, the variations of the pitch of a musical instrument,or other sounding body. In many persons the perception of sound is defective; so that, whatever may be the purity and intensity of their notes as single uncon nected musical sounds, they can never be used for musical purposes, that is, for sounds succeeding each other at regular intervals, governed by fixed rules. Many persons can imitate the voices of birds and beasts, and diversify the character of their tones to an in definite extent. These performances illustrate the perfection of the human voice, but the artifices by which they are effected have no reference to the subject under investigation. The musical varieties of the human voice are classed according to their pilek, or the middle note of their primary register, which depends on the dimensions and physical constitution of the vocal ligaments. These varieties are, the Bass, the Tenor, the Contralto, and the Soprano * ; the usual compass of each kind in the adult is represented in the annexed table.
In addition to these characteristic and prin cipal divisions of the voice, there are certain others, called the Baritone, the Mezzo-soprano, and the Soprano-sfogato, which are subdivisions of the foregoing, and the place of either of which in the scale is indicated by its name. We see by this table what an extensive variety of harmonious sounds may be produced by the combinations of the different kinds of voice. In ordinary singers the range seldom exceeds two octaves, except in those endowed with a falsetto. There have been some celebrated singers, such as Catalani, Malibran, and others, as hose compass has even exceeded three octaves, but such instances are rare. The voices in both male and female are nearly of the same pitch until the age of puberty, at which period the voice of males sinks an octave. This change of pitch is owing to a sudden enlargement of the larynx, the antero posterior diameter of which is augmented by from one-fourth to one-third, with a simul taneous lengthening of the vocal ligaments. During this process the voice is hoarse, and there is a temporary inability to regulate it. Eunuchs do not undergo this change. Ben nati is of opinion that the voice should not be exercised at this time of life, and in support of his views he cited the cases of Donzelli and Donizetti, of whom the latter lost his voice by singing, whilst the former retained it by abstaining from singing at that period, There are, however, many examples of per sons possessing fine voices, who never paid the least attention to this rule.