Emission of the Chest Voice
“If we emit veiled and feeble sounds, the larynx opens at the notes do re me (c d e), and we see the glottis agitated by large and loose vibrations throughout its entire extent. Its lips comprehend in their length the anterior apophyses of the arytenoid cartilages and the vocal chords; but, I repeat it, there remains no triangular space.
“As the sounds ascend, the apophyses, which are slightly rounded on their internal side, by a gradual apposition commencing at the back encroach on the length of the glottis, and as soon as we reach the sounds si do (b c¹) they finish by touching each other throughout their whole extent; but their summits are only solidly fixed one against the other at the notes do re (c♯¹ d¹). In some organs these summits are a little vacillating when they form the posterior end of the glottis, and two or three half-tones which are formed show a certain want of purity and strength, which is very well known to singers. From do re (c♯¹ d¹) the vibrations, having become rounder and purer, are accomplished by the vocal ligaments alone, up to the end of the register.
“The glottis at this moment presents the aspect of a line slightly swelled towards its middle, the length of which diminishes still more as the voice ascends. We also see that the cavity of the larynx has become very small, and that the superior ligaments have contracted the extent of the ellipse to less than one-half.
“Thus the organs act with a double difference: 1. The cavity of the larynx contracts itself more when the voice is intense than when it is feeble. 2. The superior ligaments are contracted, so as to reduce the small diameter of the ellipse to a width of two or three lines. But however powerful these contractions may be, neither the cartilages of Wrisberg, nor the superior ligaments themselves, ever close sufficiently to prevent the passage of the air, or even to render it difficult. This fact, which is verified also with regard to the falsetto and head registers, suffices to prove that the superior ligaments do not fill a generative part in the formation of the voice. We may draw the same conclusion by considering the position occupied by the somewhat feeble muscles which correspond to these ligaments; they cover externally the extremity of the diverging fibres of the thyro-arytenoid muscles, and take part especially in the contractions of the cavity of the larynx during the formation of the high notes of the chest and head registers.