One student recently asked me about whether the soft palate should be up all the time or not. I have not been particularly obsessing about the soft palate because I deal with it in terms of vowel quality, that is to say as part and parcel of a larger resonance concept. Yet there is a good reason why so many teachers swear by conscious control of the soft palate. When phonation is unbalanced, one of the immediate by-products is a slightly droopy velum, causing slight nasality. I find that this is also connected with excessive medial pressure, which also leads to a raised larynx. Often taking care of one takes care of the other. The point is that they are caused by the same thing, namely imbalance in the phonation mode.
In most cases I would suggest that one deals with the root cause, which is to say, phonation. However, there comes a point when phonation is near enough balanced that a thought to the soft palate could be the tipping point that yields real pressure/flow equilibrium. The question is how to get the soft palate raised or properly adjusted (for it must be flexible–It changes as the vocal tract changes resonance and with pitch change)! Many exercises are possible including a pre-yawn sensation, preceding a vowel withe the sound of “ng” in the word “sing” or simply concentrating on the quality of the vowel. The completeness of a vowel sound depends on three factors: 1)the source tone, which is the primary factor (without an efficient tone, vowels sound dull or strident) 2) Tongue and lip shaping, which respond to accurate conception of the vowel sound and 3)the dimensions of the vocal tract (i.e. vowel space).
Dealing with “vowel space” alone, without a thought to vowel conception and source tone can lead to a hollowness that the Italian masters call voce ingolata (swallowed voice). In those situations, some teachers will insist that the soft palate is down. This is not always the case. The lack of brilliance in such a situation is not so much related to resonance adjustment as much as it is a consequence of loose phonation. In a sense, phonation and vowel conception should be dealt with first before issues of resonance space are dealt with.
Similarly, I was working with a student who made remarkable improvement in dealing with a pressed middle voice. This mezzo-soprano had developed a very even and full range except for the area F4 and below. That part of her voice had improved as well, but it seemed fragile and unable to withstand increased breath pressure. Having accomplished what I felt was good coordination at the laryngeal level, I was momentary at a loss why that part of the range was so much weaker. I became aware that her jaw (we had addressed releasing the jaw because it was very tight in much of the range), although released downward, was also pushed backwards. Upon suggesting that she allows the jaw to release a slight bit forward, there was a much fuller sound in the lower range and a much smoother transition from middle to low. In the “pushed-back” jaw position, it seemed to me the larynx was being cramped and consequently the natural lower pharyngeal space was compromised. This was less the case in her middle range and certainly not the case in her upper range, where she had a more natural jaw release.
Although the problem was existent also in the middle range (though less pronounced) it did not affect that range considerably. I believe it is because the middle range is second-formant-dominant. I believe the second formant is more dependent upon the upper pharyngeal space. Indeed both vowel formants are affected by lower pharyngeal cramping, but the first formant suffers more (This is an assertion from observations in the studio and not a scientifically supported fact). Proceeding from this theory, it makes sense then that the notes that are first-formant-dominant in the low range (suffering from laryngeal cramping) would be the most compromised. Indeed that was the case. The improvement in the sound after the jaw adjustment does suggest that inappropriate jaw release can have a detrimental effect on lower notes event in cases where phonation balance is possible. The inadequate resonance adjustment due to tense jaw can alter phonation pronouncedly in otherwise balanced laryngeal function. I also believe that such jaw tension is often compensatory when laryngeal function (CT-TA-IA balance) is inadequate. In such circumstances, it may be difficult to deal with the jaw tension before phonation balance has been achieved, at least with occluded continuants (e.g. [v], [z], [m] [n], etc). The ability to produce clear and present occluded continuants is a sign of laryngeal balance (caveat: A different balance is necessary for each note. Therefore, balance in one part of the range does not mean balance throughout. Indeed one note may be perfectly balanced while the chromatic neighbor may suffer imbalance).
To summarize, it is my opinion that dealing with the soft palate and/or jaw tensions when phonation imbalance is extreme may not yield sustainable results. However when near-balance has been achieved in the phonation mode, a slight jaw or palate adjustment can be the tipping point to peak efficiency.