Vocal Tract

The vocal tract is a container of air that starts from the top of the vocal folds and goes all the way to the edge of the lips.

The average length of a vocal tract ranges from around 14-17 cm

Here are some more labels to get you acquainted. Notice that the vocal tract can feed into the esophagus, when swallowing food and liquids, or into the trachea for breathing in and out.

During swallowing the larynx is squeezed upwards to make room for food passing down into the esophagus behind it. We'll talk about how this reflex relates to singing a little later.

The vocal tract acts as a resonator (resonate= to resound) and a filter for all parts of the sound created by the vocal folds.

All sounds created by the vocal folds must pass through the vocal tract before we can hear them. We never hear the vocal folds raw sound on its own.

Except --- in this cool video. Scientists created vocal fold simulators and added different vocal tract shapes on top of the simulator to see the effect on the sound. The vocal folds on their own sound like an unintelligible buzz-tone, making us realize how crucial the filter/resonator is to making our sound beautiful and understandable.

Almost every instrument has a resonator. Any container of air that amplifies part of the vibrations counts. The voice has a unique resonator because it can actively change shape.

The air inside the body of the guitar acts as a resonator for the vibrating strings. Once the guitar is built, the resonator's shape is fixed, unlike the vocal tract.

Vertical Divider

There are multiple muscle groups that can change the size and shape of the vocal tract.

These muscle groups variously make the vocal tract longer, shorter, give it a wider opening, or firm up its walls.

Every time the size and shape change anywhere along the container of air, the change has an effect on what parts of the original sound are amplified or filtered out.

View a 3D model of the vocal tract.

how we adjust the vocal tract

For each part of the vocal tract we'll talk about ~

1.How it moves
2. How this affects the size and shape of the vocal tract
3. How that size and shape affects the overall sound output, or the "pitch of the air" in the vocal tract
(This can be a confusing concept, see our Harmonics vs. Formants page for a full explanation)
4. How you can feel this part of the vocal tract (or rather, if you can feel it)
5. Exercises to try

lips

The lips are moved by a circular muscle group that descends half way down the chin and all the way up to the nose. They can also be moved by muslces inside the cheeks (the buccinator muscles)

If the lips come forward (like for the spoken vowel /o/) the vocal tract becomes longer. The pitch of the air in the vocal tract will be lower and the overall sound may be perceived as darker.

If the lips spread (like in a smile) the vocal tract becomes shorter. The pitch of the air in the vocal tract will be higher and overall sound may be perceived as brighter.

The lips can also suck in and cover the teeth.

A narrow embouchure (or mouth shape) made by the lips can have acoustic benefits similar to SOVT exercises (see SOVT page for more information).

The lips are easy to key into because you can touch and see them. Use a mirror to check out what they're doing.

If you're interested in more forward lips for perhaps a darker sound, try putting a finger out in front of you and see if your lips can gently touch it while singing different sounds. Almost like trying to fog up a window.

For clearer consonant articulation, gently put two fingers between your cheeks to bring the lips forward. The muscle groups surrounding the lips will have to work harder and more efficiently.

tongue

The tongue is arguably one of the most instrumental articulators in the vocal tract. If all other articulators are held still besides the tongue, most vowels and consonants are still intelligible.

The tongue is comprised of 8 different muscles, is one of the strongest muscles in the body, and one of the more complex parts of the vocal mechanism. It is situated at the bass of the chin, so a resting tongue is a forward tongue. The hump of the tongue plays a strong role in determining which harmonics are accentuated, and therefore which vowel we perceive.

The tongue’s size and position in the mouth is hard to perceive. You may be able to feel where the tip of it touches your teeth, but there is so much more to the tongue’s mass than we can see and directly feel. It's important to remember that all of the muscles of the tongue can engage separately of the others. The tongue can move forward and backward at the same time.

Physical effects on our sound: If the tongue is retracted and the muscles by the hyoid bone are contracted, it can contract the space around the larynx, making free vibration impossible for the larynx.

Acoustic effects: If the tongue is forward, the space behind the tongue is large and the space in front of it is small. This can be a useful acoustic combination for many singing styles.

A high tongue hump has an acoustical benefit (shaped like a slide like for the consonant cluster ‘Nngg’=[Ng]). This shape can help focus the energy on what harmonics are highlighted, bringing more clarity to the sound.

The tongue root, at the base of the tongue, contributes to the narrowing of the epilarynx tube, and therefore, to inertance and overall vocal fold stability. Of all phonemes, the retroflex R ([ɹ]) most activates the tongue root. Listening for [ɹ] in the sound, therefore, encourages tongue root engagement.

Exercises to try: Habituate a new resting position for the tongue. Let your tongue rest on the roof of your mouth. Notice what that feels like. Let it remain there. Every time you think about it, encourage your tongue to rest on the roof or your mouth. Eventually, that resting position will become a new habit. A tongue that rests on the roof of the mouth relieves tension from the tongue and jaw.

Nnnngggg-- Aaahhh=[Ng]-[a] Use the high tongue hump of the Nnngg consonant cluster to inform a high tongue hump for other vowels like [a].

Tongue thrusts – Get your tongue all the way out of your mouth like a big cat yawn. Sing with your tongue falling over the bottom teeth and notice if it wants to pull back. If it does, this will signal that you're trying to use other parts of the tongue to help the tongue root. Listen for [ɹ] to help the tongue root engage to narrow the epilarynx tube separately from the rest of the tongue.

View muscles of the tongue.

pharynx

The pharynx, commonly called the throat, is the space behind the tongue, oral cavity and nasal cavity, and above the larynx and esophagus. View a 3D model of the vocal tract.

The size of the pharynx is mostly altered by a series of constrictor muscles. (Although it also changes size based on tongue and larynx heights). These pharyngeal constrictor muscles can only do one thing – constrict. Which tells us the pharynx is as large as it can get when it is at rest or in a neutral state. The spine makes up the back wall of the pharynx so it is physically impossible to make any more ‘space’ in the back than is already there.

During swallowing, the pharynx narrows and constricts and pushes the larynx upwards so that food can slide down the esophagus. So much of singing coordination is about contradicting this reflex. The narrowing and squeezing of the pharynx, like in swallowing, is often what singers describe as a tight and pinched feeling.

When the pharynx is open (or not-constricted like for swallowing), the vocal tract will be larger and the pitch of the air will be lower and the overall sound may be perceived as darker.

If the pharynx is constricted, the vocal tract will be smaller and the pitch of the air will be higher, and the overall sound may be perceived as brighter.

Can you feel it? The pharynx is deep enough inside the body that it is difficult to feel it directly. When a strong sensation in the pharynx occurs it is often from tension or a muscle getting tired, or from an acoustic experience. Often times when people try to feel it ‘open’, they mis-map the sensation and end up adjusting other muscles to align with their new map. When the pharynx is neutral and the most open and released it can be, singers often describe a feeling of ‘nothingness’ or ‘emptiness’.

Exercises to try: Drink a glass of air - Imagine you are holding a glass of water, bring it up to your lips and notice any sense of release behind the tongue.

Imagine the beginning of a smirk or polite yawn.

Ken Bozeman's Kinesthetic Voice Pedagogy explores these concepts further.

larynx

The larynx is a series of cartilages that sits on top of the trachea, or the windpipe. The vocal folds, the vibrating part of our instrument, are housed inside. The larynx is attached to one bone, the hyoid bone, which is the only floating bone in the body. It is therefore a very mobile structure. See our inside the larynx page for more information.

There are muscles above the larynx that move the larynx upward (suprahyoid) and muscles below the larynx that move the larynx downward (infrahyoid). These extrensic muscles play a small role in the creation and adjustment of sound from the vocal folds.

When the larynx is pulled down (as in yawning) the vocal tract becomes longer. This creates a lower pitch of the air (lower formant frequencies).

When the larynx is pulled up (as for swallowing) the vocal tract becomes shorter. This creates a higher pitch of the air (higher formant frequencies).

It seems that most instructors are able to agree on the following in regards to larynx height:
-Excess raising or lowering of the larynx impedes free vibrations coming from the larynx.
-Whatever height the larynx is at, stability in that height is acoustically ideal. A sudden leap in the larynx when going higher in the range will give uneven feedback to the vocal folds.
However, instructions that assume one has micro-control over larynx position can be tension-inducing (e.g. “Keep the larynx completely still” “Tilt the larynx 40 degrees” etc.).

Can you feel it? We cannot feel the muscles inside the larynx or the vocal folds themselves. We can feel the extrinsic muscles that move the larynx up and down, especially if they get tired or are held too long.

Exercises to try: Pharynx narrowing and larynx raising are part of the same swallowing reflex – the larynx raises because the pharynx squeezes in and pushes it up. When engaging in pharynx-relaxing experiences, notice that the larynx also avoids movement.

Imagine being surprised by some good news and making a silent gasp.

For stability in larynx height from low to high notes, breathe in the shape of the top note. Being prepared for it early in the breath will help avoid a sudden leap.

jaw

Training the jaw to relax and lower as needed has a lot to do with body awareness. Most people habituate the use of certain less-helpful muscles to help with balance. Jaw muscles often engage to compensate for weaker, larger muscles. We recommend that you explore the jaw muscles through self massage, to get a sense of where they are and how tight they are, and then through the centering exercises found on our Breath page to start. Body mapping and larger muscle body awareness will lead to relieving pressure on the jaw muscles, as can habituating a high tongue resting position.

Figuring out how to drop the jaw without engaging the chewing muscle (or the masseter muscle) is a huge coordination in singing. Bring your teeth together and bite down and notice the bulge in the back of your cheeks. That’s the masseter muscle. It has a huge job for breaking down our food, but is less helpful when it comes to letting go for singing. An easy, inward cheek smile can help to free the masseter, much like the one that Mona Lisa has.

Acoustically – when the jaw is more dropped, the vocal tract is shorter, has a wider opening and the pitch of the air is higher (the formants raise).

When the jaw is more closed, the vocal tract is longer, has a more narrow opening, and the pitch of the air is lower (the formants lower)

Adjustments to jaw position relate directly to acoustic choices and what harmonics a singer would like to boost in their range.

Can you feel it? Most people can feel jaw tension accumulate over time, but even chronic tension can start to feel ‘normal’. When it’s dropped and released, most people describe a sense of nothingness, ease and lack of sensation. Trying to force the jaw open can have complicated effects.

Exercises: Massage circles coming towards your lips on the masseter muscle.

Jaw independence: notice with a mirror or a hand on your face if when the pitch changes your jaw makes a sudden movement, like chewing.

Try looking at Mona Lisa, focusing on a centered breath, and asking your body to mirror her facial expression. Do you notice a lifted feeling in your cheeks, and a slight release in your jaw?

soft palate

The soft palate is a portal to the nasal cavity. You can feel where it begins by running your finger or tongue along the roof of your mouth. Where the bony hard structure stops (the hard palate) and the soft tissue begins is the soft palate. In this 3D model of the vocal tract, notice the soft palate is lowered and the portal to the nose is open, meaning sound can go into the nasal cavity.

There are several muscle groups that raise and lower the soft palate. During swallowing it naturally raises to keep food and liquids out of the nasal cavity. During speech it moves up and down freely to create different vowels and consonants. Nasal consonants like /m/ and /n/ require that it lower so that sound gets filtered by the nose. Certain languages like French have nasal vowels, and therefore more nasality in the vocabulary overall than languages like English.

If the soft palate is raised, acoustic information stays in the pharynx and oral cavity. If it lowers, some acoustic information enters the nasal cavity and is dampened by the wet nasal cavity resonator. The nasal cavity is not considered a ‘viable resonator’ when it comes to creating maximum volume (see Resonance page).

Sending sound through the nose (lowered soft palate) can feel great to the singer because of the amount of feedback that occurs. Many singers will start their warm ups with sound like /m/ and /n/ because of the SOVT benefits (see SOVT page for more info).

The sensation of lifting the soft palate can be depended on heavily in voice instruction, and can create misleading results. So many different sensations and muscle interactions happen around the soft palate, and it's hard to feel the soft palate by itself.

The idea of nasality is one of the most consistently mismapped concepts around voicing. What most people refer to as nasality can more accurately be explained as the acoustic element of twang (a boost in the 2500-4000Hz region). Nasality and Twang are mutually exclusive. Each can exist with or without the other one. Both have sensations around the soft palate, which leads to the mismap. Sadly, nasality is often considered to be a negative quality. Nasality represents another vocal choice. Some people use it a lot, some less often, but everyone uses nasality.

Can you feel it? The soft palate moves with subtlety, almost absent of sensation. People often mismap the soft palate for the sensation of the tongue pulling back, in an effort to create more ‘space’.

Go back and forth between an /m/ and a /b/ sound. During /m/ the soft palate is lowered, during /b/ the soft palate is raised. Feel the difference? It is verrrry subtle.

You can always tell if the soft palate is raised by plugging your nose. If the sound changes or you feel a strong presence with the nose plugged, the soft palate is lowered and sound is moving through the nose cavity.

other cool things

The vocal tract is made up of lots of pockets of air
We can think of the vocal tract as a column of air. In reality, it is hundreds of air pockets interacting, each of them with their own individual frequency boost. That’s how complex our instrument is. Here are some ways people brake it down--

Each formant of the vocal tract amplifies a given frequency band and dampens others. They are all mobile, and each formant can adjust which pitches it amplifies within around 1000Hz. The higher the frequency band that the formant amplifies, the smaller the pocket of air that makes the formant. Several of the smaller pockets of air in the vocal tract, one of them directly above the vocal folds, account for the upper formants. These have varying acoustic and perceptual impacts on a vocal signature. See the Ring/Ping/Twang and Filtered Listening and Vocal Regions pages for more info.

Density of walls also affects the sound
The density of the walls of a resonator also determine the frequencies that are brought out of the sound. If the walls are soft, the energy will be spread out over many frequencies. If the walls are harder, more energy will be given to a few frequencies. (The official concept is called Formant bandwidth or Q Factor). When the muscles around the vocal tract are flexed, there are harder walls on the resonator. Like much of what we learn to predict about the voice, wall density has to be reverse engineered because we have no direct way of feeling it.

It's wet and squishy in there
We have a unique resonator compared to other instruments for a lot of reasons – one being that ours is wet and spongy inside. This can also affect the pitch of the air inside the vocal tract.

EVERYTHING feeds back to the vocal folds
The vocal tract creates acoustic back pressure, or, energy that returns to the vocal folds instead of leaving the vocal tract. This energy is essential to vocal fold vibration as it balances breath pressure from the lungs. It is measured through the concept of inertance. This is why we prefer the term "acoustic support" to "breath support."

Resonant strategies of the vocal tract can create favorable back pressure such that the person's target muscle engagement is supported. In these cases, singing feels intuitive, engaged, and possible. Other resonant strategies can lead to less favorable back pressure. In such cases, the body has to call on more muscle engagement and/or other muscles, or it simply stops working for that target. Learning what resonant strategies create the coordination necessary for different artistic targets takes time and awareness. See our Inside the Larynx and Acoustic Strategies pages for more.

Tiny physical adjustments make huge acoustical differences
A millimeter movement of the tongue, or a slight spread of the lips, and a whole new sound is created with a different acoustic signature. It makes the coordination process a very fine-tune learning experience – but, it also means we have so many options for the sounds we want to make! – with just the tiniest of adjustments.