I have often talked about “occluded” consonants here and have included [v], [z] and rolled [r] in my exercise regimen here on the blog in addition to lip trills. Occlusion can be defined as obstruction, or closure. In terms of voice, the specific mechanism involved with occluded consonants has logical and positive ramifications relative to vocal training. My work over the past couple of years has shown interesting results particularly with tenors who sang as baritones and dramatic coloraturas having to develop a strength in the top voice relative to the fullness of their middle voices. It is not that those voices are special relative to the subject at hand but rather that in both cases there are specific challenges relative to muscular retraining.
First the mechanism of occluded consonants. Let us take [v] for example! To produce a [v] that is both clear in tone and with enough air pressure to vibrate the lower-lip-upper-teeth juncture requires a near-perfect fold posture because a clear tone requires well-adducted vocal folds and the air pressure required in the buccal cavity (mouth) to vibrate the [v] formation at the lips-teeth juncture must be elevated. In order for the air pressure to be elevated, it must be able to flow enough through the firmly adducted glottis. These are the qualities necessary for ideal flow phonation. Therefore, the ability to sing a perfectly clear and vibrant [v] is a confirmation of a near-perfect phonation mode. In short, the ability to produce a perfect [v] on every tone is the sign of a voice that is strong throughout. But it does not constitute ideal strength. Ideal strength would be the ability to produce the [v] without great muscular stress. To do this means that the [v] set-up must be so strong that it does not cause any effort.
For that reason, before the singer can produce a [v] that is clear and vibrant, the fold posture must be trained near enough to proper balance such that the [v] posture is near possibility. The [v] in particular is in my opinion a tool for the final phase of study. However, a full-voiced lip trill can bring the folds near enough to proper balance that the [v] can be achieved afterward. How long it takes to achieve near posture through lip trills depends on the singer’s personal strength levels in the relevant muscles (particularly, CT,TA and IA).
Three things should be kept in mind relative to occluded consonants which include pretty much all voiced continuants (e.g. m. n, z, r, l, etc. Partial occlusion as in [l] is less effective, but rolled [r] is very helpful because of the air pressure required to maintain it): 1) Clarity of glottal tone and strong air flow through the occlusion is crucial. There fore 2) If done too early (i.e. before the muscles are ready to produce the correct coordination, exercises on occluded consonants can be frustrating for the singer. 3) On the positive side, when the singer has near precise coordination, occlusion can bring them to ideal balance.
Yet, every singer probably a part of his/her range that is relatively balanced. In that range, do a five-note scale on a strong vibrant, clear [v], then repeat the exact same exercise on [a]. The singer should feel an immediate precision and ease on the [a] scale after the occluded scale. The goal is to carry this coordination throughout the range. When the singer reaches an unbalanced area, it will become difficult to do the exercise. A full-voiced [v] is often not possible in the upper range with singers who sing very well. It is because we are prone to accept a high note that sounds secure even if it is out of balance. The high range even among top singers is often thinly produced and therefore pressed. Occlusion exercises would induce the air flow that would bring the folds to balance by reducing medial pressure by increased airflow, which logical will require a thickening of the fold mass to maintain pitch. This would change the balance of the antagonism between CT-TA. This is less immediate with the tendency for looseness in the lower range. Looseness in the lower range can be remedied by occlusion if the middle range is already balanced. A strong vibrant and clear [v] produced in the middle range can be gradually brought down to the loose lower range. The balance of the middle would encourage a similar balance in the lower range. It can be argues that the singer can simply do exercise that increase medial pressure in the loose range. This is true. However, occlusion maintains a level of airflow that would protect against pressed voice as would occur with exercises that deal with glottal closure alone.