MECHANISM OF THE PRODUCTION OF THE VOICE. 557 



cult to find an entirely satisfactory explanation of the different tones produced by 'the 

 human larynx in the action of the intrinsic muscles than to describe the changes in the 

 tension and relations of the vocal chords. These muscles are concealed from view, and 

 the only idea that we can have of their action is by reasoning from a knowledge of their 

 points of attachment, and by operations upon the dead larynx, either imitating the con- 

 traction of special muscles or galvanizing the nerves in animals recently killed. In this 

 way, as we have seen, some of the muscular acts have been studied very satisfactorily ; 

 but the precise effect of the contraction of certain of the muscles, particularly the thyro- 

 arytenoids, is still a matter of discussion. 



In the production of low chest-tones, in which the vocal chords are elongated and are at 

 the mininum of tension that will allow of regular vibrations, the crico-thyroid muscles are 

 undoubtedly brought into action, and these are assisted by the arytenoid and the lateral 

 crico-arytenoids, which combine to fix the posterior attachments of the vibrating liga- 

 ments. It will be remembered that the crico-thyroids, by approximating the cricoid and 

 thyroid cartilages in front, have a tendency to remove the arytenoid cartilages from the 

 anterior attachment- of the chords. 



As the tones produced by the larynx become higher in pitch, the posterior attach- 

 ments of the chords are approximated more firmly, and at this time the lateral crico- 

 arytenoids are probably brought into vigorous action. 



The function of the thyro-arytenoids is more complex ; and it is probably in great 

 part by the action of these muscles that the varied and delicate modifications in the 

 rigidity of the vocal chords are produced. 



The remarkable differences in singers as regards the purity of their tones are undoubt- 

 edly due in greatest part to the unswerving accuracy with which some put the vocal chords 

 upon the stretch ; while, in those in whom the tones are of inferior quality, the action of 

 the muscles is more or less vacillating, and the tension is frequently incorrect. The fact 

 that some celebrated singers can make the voice heard above the combined sounds from a 

 large chorus and orchestra is not due entirely to the intensity of the sound, but in a great 

 measure to the absolute mathematical equality of the sonorous vibrations and the com- 

 parative absence of discordant waves. Musicians who have heard the voice of the cele- 

 brated basso, Lablache, all bear testimony to the remarkable quality of his voice, which 

 could be heard at times above a powerful chorus and orchestra. A grand illustration of 

 this occurred at the musical festival at Boston, in 1869. In some of the solos by Mme. 

 Parepa-Rosa, accompanied by a chorus of nearly twelve thousand, with an orchestra of 

 more than a thousand and largely composed of brass instruments, we distinctly heard the 

 pure and just notes of this remarkable soprano, standing alone, as it were, against the 

 entire choral and instrumental force ; and this in an immense building containing an 

 audience of forty thousand persons. The absolute accuracy of the tone was undoubtedly 

 an important element in its remarkably penetrating quality. In the same way we explain 

 the fact that the flute, clarinet, or the sound from a Cremona violin, may be heard soaring 

 above the chords of a full orchestra. 



Action of Accessory Vocal Organs. A correct use of the accessory organs of the 

 voice is of the greatest importance in singing ; but the manner in which these parts per- 

 form their function is exceedingly simple and does not require a very extended descrip- 

 tion. The human vocal organs,' indeed, consist of a vibrating instrument, the larynx, 

 and of certain tubes and cavities by which the sound is reenforced and modified. 



The trachea serves, not only to conduct air to the larynx, but to reenforce the sound 

 to a certain extent by the vibrations of the column of air in its interior. When a power- 

 ful vocal effort is made, it is easy to feel, with the finger upon the trachea, that the air 

 contained in it is thrown into vibration. The structure of this tube is such that it may 

 be elongated and shortened at will. In the production of low notes, the trachea is 

 shortened and its caliber is increased, the reverse obtaining in the higher notes of the 



