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Semi-occluded vocal tract postures and their application in the singing voice studio.

MANY SINGING TEACHERS, voice therapists, and acting voice teachers employ semi-occluded vocal tract postures in their teaching. These postures can be divided into three basic types:

1) postures where the semi-occlusion remains consistent over time

a) singing vowels into a straw

b) sustained phonation of voiced fricative consonants, such as /v/

c) sustained phonation of nasal consonants, such as /m/

2) postures where the occlusion is oscillatory

a) lip buzz

b) raspberry

c) rolled /r/

3) postures where the semi-occlusion or occlusion is very transitory

a) semi-vowels /j/ and /w/

b) voiced stop consonants /b/, /g/, /d/

Many of these semi-occluded or flow-resistant postures are an integral part of what Lessac, Verdolini, Titze, and others have referred to as "resonant voice" training.

There are a number of reasons why these postures have been so widely used. Potential physiologic and acoustic benefits of these semi-occluded vocalizing postures include:

1) A high ratio of vocal output to vocal fold vibration amplitude. As Ingo Titze has written earlier in this column, these postures tend to encourage what is known as a high maximum flow declination rate, which is to say the vocal folds cut off the air flow very quickly each vibration cycle. It is this rapid shutting off of the flow that excites higher frequencies. Moreover, these postures achieve this rapid shutting off of the flow with relatively low vocal fold vibration amplitude. The result is more bang (acoustic output) for fewer bucks (low effort and reduced risk of tissue damage).

2) Some semi-occluded postures may encourage a narrowing of the epilaryngeal outlet, which may aid the production of the singer's formant cluster and may aid in matching the glottal impedance with the input impedance of the vocal tract.

3) Improved breath management. A vocalist can engage greater thoracic and abdominal "support" without using a pressed phonation.

4) Lowered phonation threshold pressure. The positive pressures above the glottis lower the pressure needed to initiate and sustain phonation.

5) "Head voice" sensation is encouraged. This may be the most immediately tangible aspect of these postures in the voice training studio. This is due not only to the sympathetic vibration of the oro-facial tissues and sinuses of the face and skull, but also to a coupling of the vibration of the upper surface of the vocal folds with acoustic pressures above the glottis.

6) A higher ratio of thyroarytenoid muscle activation to cricothyroid muscle activation during and after use of the semi-occluded postures. This is similar to that which has been found when contrasting "covered" singing with "open" singing.

With these potential benefits in mind, the authors decided to examine what typically happens pharyngeally and laryngeally during each type of semi-occluded posture. Videoendoscopic images of the pharynx and vocal folds were taken of the first author (a voice teacher and tenor) by the second author while the semi-occluded postures listed in the first paragraph above were used as pilots to singing the vowels /i/, /u/, and /a/ on the pitch [E.sub.3] (165 Hz).

* /i/ was chosen for its low F1 (in close proximity to H2 at this pitch) and for good access to visualizing the vocal folds

* /u/ was chosen for its low F1 (in close proximity to H2 at this pitch) and as a contrast to /i/ (more lip rounding than /i/)

* /a/ was chosen to complete the series of "corner vowels" and as a contrast to /i/ (tongue less fronted)

The sequence of postures and vowels performed are found in Table 1. Streaming video of the endoscopy can be found at the following URL: Colfa/MUS/JNix/Nix_ASA.rm

From a voice training perspective, some of the practical benefits of the semi-occluded postures include:

1) Sensations of increased or at least a more steady respiratory support. The upstream resistance gives the singer's respiratory system something to work against.

2) Sensations of vibration in the oro-facial area, particularly while doing the voiced fricatives, the nasals, the lip buzz, raspberry, and rolled r.

3) Release of habitual tensions in the tongue, lips, and jaw, particularly while doing the oscillatory and transitory semi-occlusions.

4) Release of inhibitions. Doing a number of these postures requires the singer to be more extroverted and to do something somewhat ridiculous (i.e., sing with flapping lips).

5) Elevation of the soft palate. The positive oral pressure found in many of these postures cannot be generated without the palate being elevated. This is not true of the nasals, however.

6) Fronting the tongue. The voiced fricative /z/, the nasal continuant /n/, the raspberry, the rolled r, /j/ glide, and the voiced stop /d/, all front the tongue. This tongue fronting can be used to assist vowels that follow the pilot occlusions.

There are a number of possible uses of the semi-occluded postures in singing pedagogy. One approach is to perform an entire vocalise pattern or a musical phrase in a semi-occluded posture, such as a hummed /m/ or a lip buzz, then immediately perform the same pattern or phrase on vowels/text without the occlusion. One can toggle back and forth between the semi-occluded version and the "normal" version to transfer the benefits and sensations of the semi-occlusion to the vocalise or phrase. Another common approach is to use a semi-occluded posture, such as a raspberry, as a pilot to a vocalise or a musical phrase; once again, alternation of trials with and without the pilot posture can be performed to assist in the transfer of vocal production and sensation from the semi-occluded pilot posture to the sung portion.

One caveat about the use of these postures in singing training: even though from a theoretical standpoint it may be most beneficial to start with the most occluded postures and go towards those which are most "vowel-like," in the voice studio, one must often start with the postures most familiar to the student--which may only be the glides, stops, and nasals--and gradually move towards employing the more flow-resistant postures, such as the narrow straws.

In 2005, the first author participated in an experimental protocol at the NCVS laboratories in Denver which was led by Drs. Titze, Laukkanen, and Hunter.

This experiment used various flow-resistant straws (semi-occlusion type one listed above). Endoscopy was performed during that protocol as well, by Dr. Mona Abaza of the University of Colorado Hospital. Together, these two sessions have served to raise further questions about semi-occluded postures:

1) What are the similarities/differences in function within types of postures (one type of constant semi-occlusion versus another type of constant semi-occlusion, etc.)? Are there similarities/differences between types of postures (constant in general versus transitory in general, etc.)?

2) Is there any consistent change in the pharynx/larynx during the transition from semi-occluded postures to vowels? Is the change consistent within and across types of postures?

3) Which types of postures have the most change in the transition to a vowel?

4) Which have the best transfer, and how is "best transfer" defined? Is it the transfer with the least change?

5) Is there any variation in the transfer depending on vowel? It might be expected that the transfer would be easier from semi-occluded postures to the low first formant vowels.

6) Are there consistent patterns of behavior across genders, voice types, or experience levels as a vocalist?

Future studies will include systematic acoustic measurements and electroglottography of the vocal folds while semi-occluded postures are used as pilots to the vowels /i/, /u/, and /a/. Such studies may help reveal:

1) What are the similarities/differences in vocal fold contact area (VFCA) and acoustic output within types of postures (constant vs. constant, etc.)? This is especially important since one of the principal goals of "resonant voice" training is to achieve the best output while reducing vocal fold impact forces. As flexible endoscopy equipment improves, investigators will be able to see with greater precision exactly what is happening during these postures (it is hard to perform a number of these postures with a rigid scope in use), and the visual observations will be able to augment information gathered through electroglottography.

2) Is there any similarity/difference in VFCA and acoustic output between types of postures (constant versus transitory, etc.)?

3) Is there any change in VFCA and acoustic output during the transition from semi-occluded postures to vowels?

4) Is the change consistent across types?

5) Which types of postures have the most change in the transition?

6) Which have the best transfer? Is this the least change in VFCA? How can "best transfer" be defined acoustically --via changes in the spectrum, in SPL, etc.?

7) Is there any variation in transfer depending on the vowel? What about other factors, such as singer gender, voice type, experience level, and familiarity with the semi-occluded postures?

Ultimately, these studies should prove beneficial to the numerous voice therapists, singing teachers, and performers who choose to use semi-occluded postures in training sessions. They also should provide a clearer understanding of how best to transfer the benefits of these postures into speech and song.


Bele, Irene. "Artificially Lengthened and Constricted Vocal Tract in Vocal Training Methods." Logopedics Phoniatrics Vocology 30, no. 1 (June 2005): 34-40.

Miller, Richard. "What does Humming Accomplish?" Journal of Singing 52, no. 3 (January/February 1996): 49-50.

Nix, John. "Lip Trills and Raspberries: 'High Spit Factor' Alternatives to the Nasal Continuant Consonants." Journal of Singing 55, no. 3 (January/February 1999): 15-19.

Story, Brad, Anne-Maria Laukkanen, and Ingo Titze. "Acoustic Impedance of an Artificially Lengthened and Constricted Vocal Tract." Journal of Voice 14, no. 4 (December 2000): 455-469.

Titze, Ingo. "How to Use the Flow-Resistant Straws." Journal of Singing 58, no. 5 (May/June 2002): 429-430.

Titze, Ingo. "Lip and Tongue Trills--What Do They Do for Us?" Journal of Singing 52, no. 3 (January/February 1996): 51.

Titze, Ingo. "A Theoretical Study of F0-F1 Interaction With Application to Resonant Speaking and Singing Voice." Journal of Voice 18, no. 3 (September 2004): 292-298.

Titze, Ingo. "Voice Training and Therapy with a Semi-Occluded Vocal Tract: Rationale and Scientific Underpinnings." Journal of Speech, Language, and Hearing Research 49 (April 2006): 448-459.

Titze, Ingo. "The Use of Low First Formant Vowels and Nasals to Train the Lighter Mechanism." Journal of Singing 55, no. 4 (March/April 1999): 41-43.

Titze, Ingo, and Brad Story. "Acoustic Interactions of the Voice Source with the Lower Vocal Tract." Journal of the Acoustical Society of America 101, no. 4 (April 1997): 2234-2243.

Titze, Ingo, Eileen Finnegan, Anne-Maria Laukkanen, and Sanyukta Jaiswal. "Raising Lung Pressure and Pitch in Vocal Warm-Ups: The Use of Flow-Resistant Straws." Journal of Singing 58, no. 4 (March/April 2002): 329-338.

John Nix, MM, MME, Certification in Vocology, joined the voice faculty at the University of Texas at San Antonio in the fall of 2005, where he serves as Associate Professor of Voice and Vocal Pedagogy, and is creating a Voice Research Laboratory. Previously he was Director of Education and Special Projects and Coordinator of the Summer Vocology Institute for the National Center for Voice and Speech in Denver, where he worked with internationally known voice scientist and educator, Dr. Ingo Titze. Mr. Nix also has served on the music faculties of The University of Colorado at Denver and Eastern New Mexico University. He holds a Master of Music Degree in Vocal Performance from The University of Colorado at Boulder, Certification in Vocology from The University of Iowa, and has pursued additional course work towards the DMA degree. At Colorado, he studied voice and voice pedagogy with the late Barbara Doscher and the Alexander Technique with James Brody. Mr. Nix was also a participant in the 1994 NATS Intern Program, where he worked with Thomas Houser and Barbara Honn. His research has been supported by grants he has won from the National Academy of Recording Arts and Sciences, the San Antonio Area Foundation, the University of Texas at San Antonio, and two grants from the National Institutes of Health. His published articles have appeared in The NATS Journal, The New York Opera Newsletter, Journal of Singing, Vocalease, the Journal of Voice, Otolaryngology-Head and Neck Surgery, The Canadian Voice Care Foundation's Newsletter, and the Opera Journal. Mr. Nix is the editor and annotator of From Studio to Stage: Repertoire for the Voice, compiled by Barbara Doscher (Scarecrow Press, published June 2002).

C. Blake Simpson, MD, is Professor of Otolaryngology at the University of Texas Health Sciences Center at San Antonio and is the Director of the University of Texas Voice Center. His publications have appeared in such journals as Laryngoscope, Annals of Otolaryngology Rhinology Laryngology, Ear Nose & Throat Journal, Clinical Chest Medicine, Journal of Singing, Laryngoscope, American Journal of Otolaryngology-Head & Neck Medicine, and Current Opinion in Otolaryngology & Head & Neck Surgery.

Ingo Titze, Associate Editor
TABLE 1. The sequence of postures and vowels performed.

Type of
Semi-occlusion   Definition                Trials Performed

Sustained        Semi-occluded postures    Straw phonation
semi-occlusion   that can be maintained      on /i u a/
                 consistently for          Straw /i/ as a pilot to
                 several seconds without     sung /i/
                 any appreciable change    Straw /u/ as a pilot to
                 in vocal tract shape        sung /u/
                                           Straw /a/ as a pilot to
                                             sung /a/
                                           Sustained /v/
                                           Sustained /v/ as a pilot
                                             to /i/, /u/, /a/
                                           Sustained /z/
                                           Sustained /z/ as a pilot
                                             to /i/, /u/, /a/
                                           Sustained /O/
                                           Sustained /O/ as a pilot
                                             to /i/, /u/, /a/
                                           Sustained /m/
                                           Sustained /m/ as a pilot
                                             to /i/, /u/, /a/
                                           Sustained /n/
                                           Sustained /n/ as a pilot
                                             to /i/, /u/, /a/

Oscillatory      Postures where a          Lip buzz
semi-occlusion   regular cycle of          Lip buzz as a pilot
                 pressures are built         to /i/, /u/, /a/
                 up behind an              Raspberry
                 occlusion, then           Raspberry as a pilot to
                 released; the cycle         /i/, /u/, /a/
                 of pressure changes       Rolled /r/
                 is not unlike that        Rolled /r/ as a pilot
                 which takes place at        to /i/, /u/, /a/
                 the glottal level,
                 although at a much
                 lower frequency of
                 pressure oscillations
                 than occurs glottally

Transitory       Postures that are         Glides
semi-occlusion   very short in             /ji ju ja/
or occlusion     duration; can             /wi wu wa/
                 feature a brief
                 complete occlusion of
                 the vocal tract
                                           Voiced stop consonants
                                           /bi bu ba/
                                           /di du da/
                                           /gi gu ga/
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Author:Nix, John; Simpson, C. Blake
Publication:Journal of Singing
Geographic Code:1USA
Date:Jan 1, 2008
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