It is generally stated by vocal theorists that the nasal quality is imparted to the tone by the influence of the resonance of the air in the nasal cavities. In order to prove this assertion Browne and Behnke offer the following experiment, (quoted in substance): "Hold a hand-mirror flat, face up, just below the nostrils. Then sing a nasal tone; you will note that the mirror is clouded, showing that part of the breath has passed through the nasal cavities. Now sing another tone, free from the fault of nasal quality; this time the mirror is not clouded, which proves that no air has passed through the cavities in question." (Voice, Song and Speech.) This experiment is simplified by other authorities, who direct that the nostrils be pinched by the fingers, and then allowed to open by the removal of the pressure of the fingers. A steady tone is meanwhile to be sung. It will be noted, according to these theorists, that with the nostrils open the tone is nasal, and with the nostrils closed the tone is not nasal. This proves to their satisfaction that a tone passing in whole or in part through the nasal cavities must be nasal in quality.
It must be noted here that these experiments are not in any sense convincing. A tone of objectionable nasal quality can be sung equally well with the nostrils either closed or open, and so can a tone free from the nasal quality.
In theory, the mechanical prevention of nasal resonance is very simple. It is necessary only to raise the soft palate in singing, and thus to cut off the expired breath from passing into the nasal cavities. Most vocal scientists advise that the singer hold the soft palate raised for every tone.
Practical teachers of singing pay little attention to the theoretical discussions concerning nasal resonance. The overwhelming majority of teachers are firm believers in nasal resonance, and make it an important feature of their methods. They believe that this resonance is the most important factor in giving to the tone its "point," brilliance, and carrying power.
So far as instruction in the use of nasal resonance is concerned, teachers owe but little to the mechanical doctrines of Vocal Science. No voluntary muscular operation has ever been found, by which the air in the nasal cavities can be directly thrown into vibration, and so made to reinforce the tones of the voice. Instruction in the management of nasal resonance is therefore similar to that in chest resonance. The teacher describes the sensations experienced by a singer who produces the exact quality of tone desired. Use is also made of special vowels and consonants, for (supposedly) acquiring command of nasal resonance. A description of this form of instruction is given in the following chapter.
Sounding-Board Resonance
The acoustic principle of sounding-board resonance, in its application to the voice, is discussed by several vocal scientists. It is usually treated under two heads: first, the entire body is looked upon as a sounding board, capable of reinforcing the tones of the voice under certain conditions. Second, the bones of the chest and of the head are thought to be thrown into vibration, in sympathy with the vibrations of the air in the chest and nasal cavities respectively.
The importance attached by Howard to the sounding-board resonance of the entire body has already been noticed. Aside from the teachers of the Howard system, very few masters pay any attention to this feature of vocal reinforcement. Those who do so have no difficulty in dealing with the subject. When the singer stands in the position generally considered correct for singing, the body is said to be in the position most favorable for securing the benefits of this form of resonance. For this no special rules or exercises are needed.
Very little attention is paid, in practical instruction, to the vibrations of the bones of the resonance cavities. Each cavity is treated as a whole; the fact is only occasionally mentioned that the bones inclosing the cavities may vibrate, as well as the inclosed air.