I had heard this seemingly paradoxical axiom, years ago, and back then it made no sense. With time I understood there was a difference between nasal singing and the sensation of efficiency that produces a feeling of vibratory intensity in the region of the face, commonly called the mask. Yet the exact function differences that create the two results only recently became completely clear. The unsatisfying quality of nasal singing is often confused with equally irritating quality of pressed phonation. Both sounds seem to suppress low partials in favor of higher ones. At least that is the illusion from hearing.
The functions are however the opposite. A truly nasal production seems to be an attempt at remedying a lack of brilliance (squillo) in the sound that normally would occur when phonation is balanced and the vocal tract is adequately adjusted. There are three different types of fold posture/laryngeal depth possibilities: the balanced set up that produces true squillo and two others that produce an illusion of brilliance.
1. Balanced Phonation: We have already discussed the mechanism of phonation here. I wish to remind that phonation is at its simplest a two-dimensional occurrence driven by pitch. Pitch is essentially driven by the length of time it takes for one vibratory cycle to occur, which in turns determines what the listener perceives as a given pith in vibratory cycles/per minute (Hertz). Ideal fold posture includes a specific fold depth that requires ideal closure whereby the vocal folds close in such a way that breath is neither wasted nor held back (the latter would cause excessive sub-glottal pressure). Some scientists suggest that a 50% close quotient produces the most efficient results. Much higher close quotients have been recorded as acceptable among more robust voices. Indeed the distance between optimum vocal production and what is considered professionally acceptable is considerable.
2. Pressed Phonation: Pressed phonation (over-adduction of the vocal folds) occurs when the fold depth is insufficient. Too little fold depth speeds up the rate of vibrations, which means pitch would increase. To prevent a rise in pitch, the folds press together to slow down the opening of the folds. In this case the folds remain closed for long (higher close quotient) and the amount of air released is less. The result is less sound with a discernibly thin quality. It is important to remember that the shallow fold posture is not a random occurrence but rather a result of the singer’s conception of his/her own sound. Muscular coordination is a result of desire. In other words, the singer produces his/her own dysfunction without being conscious of it. When the singer then discovers that the sound is dysfunctional (whether because others do not like it or s/he begins to experience discomfort), the muscular balance had become so ingrained that spontaneous correction is usually not possible. In most cases of imbalance, a certain amount of time is required to achieve balance.
3. Nasal production: Nasal production is more complex because it is an attempt at remedying a perceive imbalance, namely a deficit in brilliance (i.e. a lack of strength in the high partials due to loose phonation). In such cases, the singer experiences a type of brightness that has no foundation in balance, but feels much more satisfying than the dullness of an unaltered breathy phonation. This kind of production gives the singer a false sense of correctness, because most of us have been told that the sound needs to be bright and forward. As I explain above, when an imbalance in the phonation process has been produced for a long time, spontaneous correction is usually not possible. However a spontaneous pacifier is possible and that is nasality. To the singer’s ear, the tone is brighter and feels more “forward” because of the nasal vibration, which the singer, who has not experienced the intense frontal sensations that accompany proper phonation, mistakes for mask resonance.
Another element in this process is laryngeal height. A high larynx is most often a result of pressed phonation, which produces increased sub-glottal pressure that the laryngeal depressors cannot sustain. However an imbalance between laryngeal depressors and levitators can produce a high larynx in the case of balanced phonation or even loose phonation. This is to say that nasality is not dependent upon a high larynx.
The remedy for nasality is better glottal closure because nasality is usually introduced to make up for the lack of brilliance that would be a normal result of balanced phonation. To induce better closure it is common knowledge that nasal consonants like [m], [n] or “ng” help bring the vocal folds closure together. A nasal vowel, for some reason does not. My guess in this case is that the nasal consonants cause an occlusion of the vocal tract, which has proven to influence greater glottal efficiency. To have an influence on phonation, it makes sense that the consonants that occlude the vocal tract must be continuants. For that reason, voiced fricatives like [v] and [z] have proven particularly effective in increasing efficiency of phonation. In the case of the nasal continuants, it would seem that their efficiency factor trumps whatever ill effects might be otherwise produced by nasality. It should be clear therefore that nasal continuants are not used for their nasality but rather for the positive effect of their occlusion. In this way, we can understand why nasal vowels do not help phonation.
It is also my observation that nasality is more common with vowels that are prone to tongue tension. When there is glottal inefficiency (either pressed or loose phonation), the tongue is often recruited (pulled back) to help reduce the resulting instability in the larynx. Because the vowel [i] is produced with a considerably elevated back-of-the tongue, it has been very helpful in inducing more efficient phonation. In other words, the muscular action innate to the production of the [i] vowel counters the retraction of the tongue that is associated with inefficiency. I should caution that the [i] vowel is not a full-proof tool. The statement above regarding a requirement of time to change imbalance is important. The [i] vowel may produce the quickest difference in the direction of efficiency, but it does not guarantee efficiency. That is why a singer can sing a very good quality scale on the [i] vowel and has a terrible time doing the same on [a]. Nevertheless, the [i] vowel over time can stabilize efficiency such that production of other vowels also become more efficient. The [u] is particularly prone to inefficiency. When dealing with breathy phonation, I would employ vowels in the sequence [i], [a], [u].