Vocalist.org archive


From:  Sally Collyer <scol8413@m...>
Date:  Fri Jul 19, 2002  12:41 am
Subject:  Registers and vocal fold function

Dear Lloyd

Thank you for a very succinct and coherent posting on registers and vocal
fold function. I would agree with much of what you have written but I do
have difficulty with the idea that the vocalis is active only in chest
voice and that resistance to the cricothyroid in head voice comes solely
from the ligament. Human physiology is based upon agonist and
antagonist: two muscles, or sets of muscles, contracting in opposite
directions to control movement finely. Both sets are active but to varying
degrees. I have always understood that ligaments cannot contract;
therefore, the vocal ligament cannot act as antagonist to the cricothyroid,
just a safety strap stops you falling further but can't pull you back
up. Were the vocalis to cease to act in head voice, would that not make
the cricothyroid unique in acting with no antagonist? It seems to me that
pitch change could then be achieved only by increasing or decreasing
subglottal pressure or airflow, which would limit the singer's ability to
'disconnect' pitch change from dynamic change. For example, if the
singer's vocal folds were now stretched to the point where the ligament was
activated, the only way to raise pitch would be to raise subglottal
pressure (may I crudely say, "blow harder") but this would also increase
loudness, so how would the singer float a high note pianissimo?

My understanding from Hirano's work is that stretching the vocal folds by
the cricothyroid acts to stretch both body and cover, so that full stretch
(such as to take up the ligament) would mean stiff cover and (without any
antagonist to the cricothyroid) no way to reduce the cover's
stiffness. Therefore, how would changes in timbre occur? If I have a
singer in my studio who is pushing too hard on high notes, I aim to have
him reduce the effort (and this applies to low and middle notes too), and I
postulate that what I am doing is both reducing the total tension (and
adductive force, as well) and changing the balance to be 'more contribution
from the vocalis, less from the cricothyroid' so that the vocal fold
tension is as required for that pitch, that loudness, that timbre but the
tension in the cover is less. That is, producing the same amount of vocal
fold tension/mass with a shorter vocal fold so that the cover is
looser. This is my understanding of different timbres on high notes. If
the vocal fold tension/mass on high notes is produced solely by the
cricothyroid with no antagonist, I cannot see a) how pitch could be
changed, b) how pitch and loudness could be separated, and c) how different
timbres could be obtained.

For completeness of discussion, I should add that stretching the vocal
folds will induce passive tension (antagonism) in the vocalis but being
passive this would not provide the active antagonist needed by every
agonist for fine co-ordination.

In brief, I believe both vocalis and cricothyroid should be active at all
times in singing and that the balance between their contributions is
significant to the timbre.

With regard to register transition during loud or soft singing, I have
always found the transition to be more challenging when singing softly than
when singing loudly. If my simplistic assumptions on vocal fold function
are fundamentally accurate, I would have to conclude that my habit during
an upward scale softly is to reduce the contribution of the vocalis too
soon, replace it with greater contribution of the cricothyroid, then
increase airflow/pressure to counteract the drop in loudness due to
decrease in upper partial energy in the source spectrum resulting from
stiffening of the cover. To say that in a more complicated way, I change
the balance from chest (which is louder, and I am careful to use the
perceptual term 'louder' here) to head too soon and short-change myself by
mistaking use of a lighter timbre with singing softer: I reduce the
richness instead of just singing more quietly.

Unfortunately, my reply is not nearly so succinct or lucid as your
posting. These are speculations based on matching what I think I know from
reading with what I think I know from working with my own voice and working
with others' voices. There are many, many gaps. Thank you for the
opportunity to wrestle a little more with this conundrum.

Kind regards

Sally





  Replies Name/Email Yahoo! ID Date  
19746 Re: Registers and vocal fold functionLloyd W. Hanson   Thu  7/25/2002  
19749 Re: Registers and vocal fold functionDomisosing@a...   Fri  7/26/2002  

emusic.com