Nasal tones are produced, not because the vibrations pass through the nasal passage, but because they are obstructed in their passage through them. A nasal tone is always a cramped tone, due to impediment, tension, or muscular contraction, particularly in the nasopharynx.
The congestion and consequent thickening of the mucous membrane lining the cavities of the nose and head, resulting from a cold, make the tone muffled and weak, owing to the inability of the parts to respond to the vibrations and add to the tone normal nasal resonance.
The elder Booth (Junius Brutus), about 1838, suffered from a broken nose which defaced his handsome visage and spoiled his splendid voice. His disability was so great that afterward he seldom played. That the cause of this impairment of Booth's voice was due to the contraction and more or less complete obstruction of the nasal passages is too evident to call for comment.
Many singers have sweet but characterless voices that lack the fulness, power, and ring they might have because they fail to avail themselves of the augmenting power of the resonance cavities. The singer must learn to habitually use all of the resonance cavities and use them simultaneously.
Lilli Lehmann, in How to Sing, says that, "although the nasal sound can be exaggerated,—which rarely happens,—it can be much neglected,—something that very often happens." The context makes clear that what in the English translation of the great singer's book is called "nasal sound" is exactly what we term nasal resonance.
After charging the monotonous quality or lack of color in the voice of a famous opera star to lack of nasal resonance, Madame Lehmann speaks of the consummate art of Marcella Sembrich who "in recent years appears to have devoted very special study to nasal resonance, whereby her voice, especially in the middle register, has gained greatly in warmth." She says further that nasal resonance "cannot be studied enough. It ought always to be employed." "How often," she says, "have I heard young singers say, 'I no longer have the power to respond to the demands made upon me,' whereas the trouble lies only in the insufficient use of the resonance of the head cavities."
From the foregoing, the conclusion follows that the head vibrations are not only an essential element, but that nasal resonance is a most important element in imparting to tone its brilliance and carrying power. Without thought of the mechanism of how nasal resonance is produced, the singer has control over it by direct influence of the will. The tones, low as well as high, should seem to start in the nose and head, and the vibrations of the perfect tone can be plainly felt upon any part of the nose and head. Without the head vibrations no tone can be perfect, for nothing else will compensate for the lack of these. Vocal organs used as here described will suffer no fatigue from reasonable use; hoarseness will be to them a thing unknown, and "minister's sore throat" an unheard of complaint. Not only is faulty voice production a source of great discomfort, but it is the cause of many diseases of the chest, throat, and head.
The gentle practice in easy range of the exercises given in the [chapter following], will do much to restore a normal condition.