A colleague recently asked me whether there is any scientific literature that certifies whether sub-glottal pressure causes the larynx to rise. Perhaps a couple of the other voice science types here can point us to articles that deal specifically with SBP (cause) and High Larynx (effect). What I did reply is that SBP is the only vertical upward force that could be responsible for the larynx climbing, therefore it might be superfluous to write a paper on this particular cause and effect. My colleague explained that he does not experience a high larynx because of SBP and that he could apply quite a bit of breath pressure to his sound without having a high larynx. Is it that his laryngeal stabilizers are stronger because he is an experienced singer? Is it that he is experiencing something different that feels to be SBP?
The answer is YES on all counts and NO on all counts. I am not being facetious! Sub-glottal pressure is what drives the voice. A healthy voice has adequate SBP that gets transformed into glottal flow! A tense voice has SBP that does not get released but continues to build up to unhealthy levels below the larynx and cause it to rise. Here is the kicker! It is not too much air from the breath source that causes unhealthy SBP but in fact too little air! Let me explain!
It is important to understand that SBP is governed by two elements, namely the air in the lungs and the resistance of the vocal folds. Any vocal sound requires compressed air. If the diaphragm does not rise adequately to provide the air pressure necessary, the vocal folds immediately make up for it by squeezing together to reduce flow and raise the pressure to necessary levels in order to keep the sound going. In such a case, the sound becomes labored because of the added stress created by the tightened larynx. The higher SBP that results and the discomfort in the throat causes a response from the brain to lower pressure even more. The diaphragm stops its rise and the throat compensates even more. A terrible snowball effect. In a sense, less air pressure from the diaphragm requires more squeeze from the throat as a compensatory measure.
In short, SBP can be either virtuous (when provided by the rise of the diaphragm, thereby keeping the laryngeal resistance appropriate) or erroneous (when provided by a laryngeal squeeze, further suppressing the healthy participation of the diaphragm in the equation).
It should be mentioned however that too much pressure from the diaphragm is also possible against a properly functioning larynx. If the laryngeal stabilizers cannot sustain the pressure, the folds can be blow apart literally. One can in fact attempt to sing too loudly, more than the native instrument can sustain healthily.
Good, consistent pressure from the diaphragm frees the vibrating edges from over-tightening. This means that the singer can reduce volume without losing necessary pressure. This is why soft, well-supported singing is tricky. The breath pressure must be reduced for softer singing, however not to the point of losing necessary pressure below the larynx. Finding the right coordination is a sensory experience and requires practice in order for all the participating muscles to learn their part in the equation.
At the root of it all is a fold posture that encourages glottal flow. This includes appropriate mass (fold depth) to avoid a necessary squeeze relative to the length of the glottal cycle. This has to do with a perception of one’s native vocal color. This is different with each voice. A lot of our process in vocal technique is discovering what our natural vocal color is! The natural color is often supplanted by learned vocal habits that the singer believe to be native. The true voice in the beginning might feel foreign. Singers have a tendency of resisting anything that feels “unnatural” to them. Paradoxically, in many cases what feels unnatural is in fact nature and what feels natural is in fact poor nurture.