Note: This article is a response to some recent Vocal Technique discussions over in the Forum. I thought this may be of some interest to ModernVocalists at large.
In developing the full range (or compass) of the voice, its important not to forget that the lower ranges need some attention, too.
The pitch control mechanism
As a general principle, lower notes of the voice are produced when the vocal bands are short/thick, and higher notes of the voice are produced when the vocal bands are long/thin. Two sets of muscles coordinate to produce the full range of these positionings.
The exercises for the lower voice are very direct, beginning on the B just a bit more than an octave below middle C. For Female voices, the B next to middle C is a good starting point. The goal of the exercises is for the singer to experience and practice vocal coordinations that have the following characteristics:
- short/thick fold configuration
- adduction adjustments with the short/thick configuration
- well-tuned notes of the lower range
- well-selected vowel shades that give best resonance in the lower range
- presence and consistency of twang, or singer's formant
The basic exercise
Beginning on the B, onset an /A/ (as in the English word 'hat'), in a bright, almost blatty pronunciation (without attempt at beauty or loud volume, only clarity), sustain a few seconds, and then convert the vowel to /a/ (ah). The first goals are to start the note well, clearly, and then make the vowel adjustment to the 2nd vowel without losing the intensity.
After the clear tone has been accomplished on the beginning note, take a breath, transpose the exercise downward by a semitone, and repeat. Make a few attempts on each note, with the emphasis on clear and bright tone, even if it is not very loud as you descend. Proceed transposing downward until you get to a vocal fry.
Rest a minute, and then go back to the B, and sing the single vowel 'Ih' (as in the English words 'mit', 'kit', 'fit'. Transpose as before.
Building consistent tone quality
The relationship of low pitch and thick cord is best stated when put this way: 'When the vocal bands short and thick, the pitch which results will be a low one.'
Consistent tone quality, though, is not so much about how thick/thin the bands are, but about maintaining consistency of some key phonation and resonance characteristics:
1) the open & closed phases of the glottal opening
2) the speed with which the glottis closes
3) shading the vowel so that the harmonics and resonances align
4) retaining ariepiglotic resonances (ring or twang, depending on larynx position in the throat).
The purpose of the deliberately thick-fold exercise is to work out the subtle changes in adduction and registration so that these other aspects do not change radically. As the folds shorten/thicken, slightly less adduction is needed. This is the inverse situation from what the singer does when going to the higher ranges of the voice, where slightly more adduction is needed to compensate for the thinning of the vocal bands.
Expressed in another way, the lowest regions of the voice have the desired tone quality consistency (connection) with the neighboring part of the voice, and the range overall, compensating for the acoustic disadvantages of the lower ranges..
What usually happens
In this low section of the voice, the tendency is to let the vocal bands get overly loose as they get shorter. This causes items 1 and 2 in my list to change... the open phase gets longer, and the bands close more slowly than previously. Working the thick fold configuration with an ear to maintaining quality helps the singer discover just the right balances of muscle action required for that region. For normally higher voice (i.e., tenors who have no trouble with high C ) this sometimes feels a bit like making the lower voice a bit more muscular or gutteral. If overdone, it will.
Similarly useful to experience is #3- the alignment of the harmonics with the resonances. Whereas the mid voice usually aligns F1 to harmonics 2 to 4 (depending on vowel,) in the lower voice F1 aligns with harmonics 3 to 6. This transition has implications for the vowel color, the sensation of the vowel in the body, and the overall vocal strength. Because harmonics 4-6 have less energy than 2 and 3 do, the tone will feel less 'fat', and will be less powerful. The compensation for this is to be certain that the glottal closed phase stays equivalent, or is even a bit longer than it is in the mid voice... in colloquial, older terms, is 'chestier', by letting the vocal bands be short, but with a little more muscle involvement.
Benefits for the voice overall
Interestingly, work in this lower area to maintain clarity and vocal strength also will affect the rest of hthe voice. This work puts the vocalist in greater awareness of the action of the shortening/thickening muscles, and registration-related sensations overall. The usual result is that finer control of the powerful top is the result, and the entire voice experiences additional strength and security.
For those interested in the muscle actions
This exercise is not so much about building strength, as it is about building a vocal coordination which has greater Thyroarytenoid (TA) involvement. Yes, some additional strength is expected when a muscle is used, but what we are really trying to do is establish a different level of balance of activity of the TA and Cricothyroid (CT). In kinesiology terms... we are exercising both sets of muscles through the complete range of motion, and encouraging a different level of activity of both as we do so.
Time to spend on the exercise daily
As to the length of doing it... 5 or 8 minutes in a practice session should be sufficient. If you want to do more, alternate each downward scale with a high voice exercise... falsetto or light head voice. This is on the other end of the range of motion... CT is contracted and TA is stretched. You can think of this as working the 'ends' of the coordinative range.
If you decide to do the alternating approach, then I'd recommend a total of about 15 mins, followed by exercises which coordinate... full-range sirens, arpeggios, messa di voce, etc., for another 10 minutes. Following that, take a few mins break, and then work on songs. This approach should lessen the issue with the mid voice exercises, as you are likely overdoing the lower part a little bit... and (as we try to keep in mind) the goal is to build the coordinated voice... the whole thing.