Saturday, September 9, 2017

A Three-dimensional Model of Vocal Fold Closure: Efficiency and Avoiding Pressed Voice

I remember years ago, when the Italian mezzo-soprano Ada Finelli told me that the muscles of Appoggio are far inside the body (not the superficial ones we see) that and their contraction produced a twisting action.  I was not sure what she meant back then, but I trusted her.  Eventually I observed graphic representation of the muscles that root  the diaphragm to the various insertion points on the pelvis and saw what could be described as a twisting motion.  Her sensations were based on empirical information although she was not aware of the science.

As for me, my process is usually instructed by the available science.  A recent article by Ingo Titze and colleagues addressed a two-prong system that produces efficient glottal closure (see more below).  The specifics of that article are a bit complex to address here, however the concept is not new.  We know that the contraction of the Lateral Crico-Arytenoids (LCA) bring the two vocal folds to midline.  This however does not complete the closure of the posterior arytenoidal juncture (sometimes referred to as the mutational chink in earlier vocal literature).  The contraction of the Inter-arytenoids (2 pairs, one lateral and one transversal) complete the posterior closure giving the singer that sensation of "mask resonance," rooted in multiple functions of breath compression, glottal resistance and resonance adjustments.

The concept of mask resonance is a a controversial one.  I address it here as a result of a three-dimensional closure system.  Many would instruct their students to "put the sound in the mask!" This directive does not always produce the desired results.  The student indeed may accomplish some kind of closure to achieve the objective, but often the result is pressed phonation.  This occurs for two reasons: 1) the directive of "put it in the mask" does not address any specific function relative to the goal. 2) Even if fold closure is mentioned as the functional means toward the end result, if closure is conceived as a simple system--one set of muscles-- the result is often hyper-function relative to whichever muscle group is targeted for closure.

The two-function system I wrote about above is the most complete we commonly hear about.  The third part of the three-dimensional system is indeed fold-depth.  Titze points out the importance of appropriate y-axis (vertical) mass relative to the "closure phase" of phonation.

Appropriate fold-depth depends on the specific voice.  Experience teachers can easily hear when a voice is "shallow"in color.  Often the recommended remedy is to "find more room"!  That directive does not specify any function other than a sound concept that is less "superficial-sounding." The easiest way to accomplish that objective is usually to retract the tongue.  This often gives the student a fall sense of room and depth, however the result is artificial darkness and a loss of high overtones.  By contrast, accomplishing appropriate depth (which must be developed over time with respect to breath/vocal fold interaction) often requires time.  But when accomplished, pressed voice is avoided, flow-phonation induces an appropriate low larynx, which increases the length of the vocal tract.  The more massive the vibrating fold-cover the more consistently stronger must the breath compression be.  This physical development (or lack thereof) is often the greatest obstacle to the singer's ability to accomplish a tone that is completely full (resonant) relative to that particular vocal material.  It is this accomplishment that gives the voice its unique acoustic signature (timbre) and optimum resonance.

The richness that comes by way of the vertical fold depth (Thyro-arydenoid function) can of course be exaggerated.  The fullness of the voice must not be so extreme as to hinder the possibility of closing the superior aspect of the folds. Nor should efficient closure at the interarytenoid level hinder the possibility of a full tone.  Yet often, in an attempt to avoid exaggeration of either function, singers often neither sing fully enough, nor achieve adequate closure. Of course both breath compression and acoustic adjustments (vowel/vocal tract) contribute to the ability to accomplish a three-dimensional fold closure model.  In short, all functions interact upon each other and in such a context are interdependent.  They must however never become co-dependent. In the former scenario, functions act upon each other but do not hinder each other.  In the latter, the singer's fear of going too far in any direction, causes him/her not to go far enough in any direction.

© September 9 2017

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