Monday, June 14, 2010

Kashu-do (歌手道): Head and Chest Voice Experiences: Fold Vibration and Muscular Dynamics

In response to the last post, Klaus says the following:
This actually brings up a key point that I've been meaning to blog about for a while. I think many people (I'm not suggesting you are one of them) conflate two different ideas which both are related to our experience of head vs. chest.





One is the vibratory pattern of the folds, which voice science tells us is different for chest and head. (There are also distinct patterns for fry and whistle.) These vibratory patterns cannot be blended--they simply switch from one to the other, though the switch can be acoustically masked.

Dear Klaus,
Thank you for bringing up this wonderful point.  Relative to fold vibration patterns, what you say above used to be the common understanding but Titze and others have proven otherwise. The vibration patterns are not as diametrical as we once believed. Indeed in a head voice driven pattern (i.e. a pattern driven dominantly by the fold cover) also shows activity in deeper parts of the folds. A simple discussion of this can be found here at the website of the Nationcal Center for Voice and Speech. 





The second is the action of the vocalis vs. the CT muscle groups. These can achieve many different balances or mixes within the different vibration patterns. Traditional male singing is in the "chest" mode, while women and countertenors sing in the "head" mode.
I think this is also a misundestaning based on literature that is now outdated.  When acoustic studies made clear the presence of two acoustic (i.e. vocal tract adjustment) events in the female voice (i.e. F1 dominance to F2 dominance around F4 and F2 dominance to F1 dominance around F5), the first and second passagi in the female voice, voice teachers sought to make a parallel muscular/fold vibration event.  Indeed, many sought to move to a "sensory" head voice. In the last generation of female opera singers, it is common to hear a middle voice lacking in thrust because the fundamental muscular balance had been compromised. Fundamentally there is no difference in the female folds when compared to male folds other than relative size. The octave differential has an acoustic significance relative to the nature of vowels.




Thus "chesty" in the sense I see you mean it above refers to muscle activity, not vibration pattern. The big question of course is does training a muscle in the "wrong" vibration mode help its strength in the right one? Ie: women singing in belty chest to "strengthen the chest" and men singing in falsetto to "strengthen the head." I don't pretend to know the answer, though I have some guesses. Are you doing exercises with her in this vein or are you sticking to a "correct" (aesthetically viable) mode of production?
What I have tried to propogate through the discussion here is a correlation between CT/TA dynamics and fold closure and by extension the vibration pattern.  Pressed voice will tend to yield a relatively )thick pattern bringing the deeper layers of the folds into the vibration in a more dominant way then would be ideal. Likewise a loose phonation induces a cover dominated pattern. Paradoxically a pressed pattern is too much CT dominant (i.e. too thin a production) while a loose phonation is TA dominant. The balance of the modal voice changes from pitch to pitch. My belief, which I believe is confirmed by the Titze studies is that the vibratory patterns are completely related to the nature of the CT/TA balance, since that balance determines fold depth and therefore the complimentary fold closure posture that determine the exact frequency of vibratory cycles.

The question you ask is the crucial one.  Relative to the recent clip in which I sing a high C, I explained that this was based on a voice that began in falsetto mode (i.e. virtually devoid of TA [vocalis] activity) three months ago.  I should specify that I mean full-closure falsetto. Although the fold posture begins totally without TA participation, as soon as the folds come together fully, the breath pressure/flow will induced vocalis activity. The increase flow will reduce medial pressure/fold contact mildly. This would be enough to speed up the vibratory cycle. Where frenquency is a constant, there has to be an adjustment in fold depth (greather fold depth) to maintain pitch, which can only occur with an increase in vocalis activity.

So I am answering affirmatively. Most voices are in an unbalanced state relative to the complex balance between all the lanryngial muscles. Changing either TA/CT activity or the medial pressure of the IAs will have a direct impact on frequency, which then requires an adjustment from the other muscles to maintain that frequency. The voice is driven by pitch in that sense.  It is not always necessary to work on one side or the other.  The crucial place to balance is the middle of the voice, around the place where dominance shifts from TA to CT, around C4 for the average male voice and C5 for the average female. If the lower voice had been produced too heavily, as we know there will be a tendency to flip to a very light production in the upper voice. In such a case, my strategy would be to induce better closure in the lower voice, which would reduce TA activity by extension. This then would prevent the sudden switch if the low is brought to balance.  There are extreme cases:



I am currently working with a singer whose voice was so vocalis dominant that at one point 8 years ago the voice dropped to the lower octave and she has not had access to the upper octave of her rangey. At her first lesson three weeks ago, her highest comfortable pitch was G4. By lessons end, after exercises to induce greater CT activity and reducing TA activity in the lower range, we coaxed her voice to Bb5, an octave and a third up.  I was not sure we would achieve that at the first lesson. When she returned the following week, it was obvious that she had practiced. But this time we achieved G5. In my estimation, the CT was fatigued from the exercises. This time however access to the middle range up to Eb5 was relatively easy. She is progressing.


Other voices are extremely CT dominant and have little low range. It is necessary in such cases to work on strengthening the vocalis. At the beginning of training, any exercise that induces strength ine the weakened muscle group is advisable. More balanced dynamics are possible once both muscle g.oups have been strengthened.




In any case, the right balance of vocalis and CT has to be found for different volumes, vowels, pitches, etc. which is clearly your goal with her as well as with every singer you blog about. Thanks for an interesting discussion
The goal is not only Vocalis//CT  balance but rather a global balance among all muscles involved. Achieving a balance between CT and Vocalis brings a balance to the nature of the closure mechanism as well (i.a interaytenoid muscles), which in turn influences breath flow, which influences fold vibration, laryngeal depth, and breathing.  What we are finding out is that vocal function constitutes a total system of interdependent muscles.

© 06/13/2010

2 comments:

KG said...

Thank you for addressing my comment in such depth. It will take me some time (which I do not have today) to go through and digest it.

However, I think we are disagreeing specifically on the first point of discussion, though I suspect it might be a question of semantics, as it so often is in singing. When I say the voice is either in chest or in head (I really should probably say falsetto, not head, but when applied to the female voice this tends to confuse people) I am referring to Robeau's 2009 article "Laryngeal Vibratory Mechanisms" in the Journal of Voice. Interestingly, upon review of his references based on your post, there is nothing by Titze referenced which was written after 1994. Could you point me in the direction of this more recent work to which you refer?

Thanks!
<a href="http://www.klausgeorg.com>Klaus</a>

Jean-Ronald LaFond said...

I agree about the semantics. I will try to find the Titze articles. I am too in a very busy mode right now. Let us continue this interesting discussion. Much to come out of it. Martin Berggren, a frequent commentator here, might have access to the Titze articles.