Three Linked Systems: Power, Source, Filter
To understand how the voice produces sound, it helps to think in three linked systems that work at the same time: (1) airflow and pressure (the power), (2) vocal fold vibration (the source), and (3) resonance and articulation (the filter). You do not “make sound” by pushing air alone, and you do not “make resonance” by forcing your throat open. Sound emerges when steady breath pressure meets flexible vocal folds, and the resulting vibration is shaped by the vocal tract into the tone you recognize as your voice.
In singing, most technical problems come from mixing up these jobs. For example, trying to get louder by squeezing the throat (source tension) instead of increasing efficient breath pressure (power), or trying to “place” resonance by pushing the larynx around rather than shaping the vocal tract (filter). Keeping the roles separate makes practice clearer: breath sets conditions, folds vibrate, tract shapes.
Airflow and Subglottal Pressure: The Power Behind the Tone
Airflow vs. pressure (they are not the same)
Airflow is the movement of air out of the lungs. Subglottal pressure is the air pressure building below the vocal folds (under the glottis). You can have high airflow with low pressure (a leaky, breathy sound) or higher pressure with controlled airflow (a clear, efficient tone). Singing generally needs stable pressure with just enough airflow to keep the folds vibrating without drying them out or blowing them apart.
A useful way to picture it: airflow is like water moving through a hose; pressure is like how much the faucet is turned on and how much resistance the hose provides. If the “nozzle” (vocal folds) is too open, water gushes but pressure at the nozzle drops. If the nozzle is appropriately narrowed and flexible, pressure can build and the stream becomes more focused.
What the body does to create pressure
Pressure comes from the coordinated action of the respiratory system: the diaphragm returns upward, the ribs and abdominal wall manage the rate of that return, and the lungs recoil. You do not need to “push” aggressively; you need steadiness. Too much sudden pressure can slam the folds, causing pressed phonation; too little pressure can cause weak onset and unstable pitch.
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Practical step-by-step: feel steady pressure without forcing
This sequence helps you experience pressure as steadiness rather than brute force.
Step 1: Silent “fog a mirror.” Exhale on a silent, warm “haa” as if fogging glass. Notice the open, easy throat feeling and the steady stream.
Step 2: Add a narrow straw shape with lips. Keep the same easy feeling but purse the lips as if blowing through a thin straw (no sound yet). The airflow will slow and you may feel gentle back-pressure at the lips. This is a safe way to sense what “pressure with control” feels like.
Step 3: Keep the straw lips and add a soft voiced “vvv.” Let the sound start gently. If it feels scratchy or tight, reduce volume and aim for a smooth start.
Step 4: Repeat on 5-second holds. Aim for consistent loudness and no wavering. If the sound fades quickly, you likely lost pressure; if it gets louder and tighter, you likely increased pressure too suddenly.
Vocal Fold Vibration: How the Source Is Created
The vocal folds are not “flapping” in the air
The vocal folds (vocal cords) are layered tissues that vibrate because of aerodynamic and elastic forces. They come together (adduct) enough to resist airflow, pressure builds below them, and then the pressure pushes them apart. As air escapes, pressure drops, and the folds’ elasticity plus the Bernoulli effect (faster airflow creating lower pressure between the folds) helps them come back together. This rapid open-close cycle creates pulses of air that become sound.
Important: the folds do not need to be squeezed hard to close. Efficient closure is balanced: firm enough to avoid excessive leakiness, but not so pressed that the sound becomes strained and the vibratory pattern becomes stiff.
Pitch: why higher notes require faster vibration
Pitch is primarily determined by how fast the vocal folds vibrate. Higher pitches require faster vibration, which is achieved by changing fold length, tension, and thickness. In general, as pitch rises, the folds lengthen and become thinner at the vibrating edge. As pitch lowers, they shorten and thicken. Breath pressure also interacts with pitch: too much pressure can drive pitch sharp or cause strain; too little can make high notes unstable.
Loudness: more than “more air”
Loudness increases when the vibration has greater amplitude and when the vocal tract efficiently radiates sound. That often involves a moderate increase in subglottal pressure and an adjustment in closure so the folds can handle that pressure without leaking or clamping. Many singers try to get loud by either blasting air (which can make the sound breathy and tiring) or squeezing the throat (which can make it harsh). Efficient loudness feels like a stable, energized breath with a responsive, not rigid, fold vibration.
Practical step-by-step: three onsets to diagnose balance
Onset is how the sound begins. Practicing different onsets helps you feel the relationship between airflow and closure.
Step 1: Breathy onset (“haa”). Start with a whispered “h,” then add voice: “haa.” Notice the airy start. This shows what happens when airflow leads and closure lags.
Step 2: Hard onset (“’aa”). Start with the folds tightly together, then release sound abruptly: “’aa.” Do this gently and briefly (one or two tries only). Notice the “clicky” start. This shows what happens when closure leads and pressure pops through.
Step 3: Balanced onset (“aa”). Start the vowel cleanly without extra air or a glottal pop. The feeling is coordinated: air and closure meet at the same time.
Step 4: Apply to a simple pattern. On a comfortable pitch, sing “ma-ma-ma” at medium-soft volume, aiming for the balanced onset each time. If it turns breathy, reduce airflow and allow slightly firmer closure; if it turns hard, reduce pressure and release the throat.
Resonance: How the Filter Shapes the Sound
Resonance is amplification and tone-shaping
The raw sound created at the vocal folds is a buzzing, complex signal. Your vocal tract (throat, mouth, and nasal cavities) shapes that buzz by emphasizing certain frequencies and reducing others. These emphasized frequency regions are called formants. You do not need to memorize formant numbers to benefit from the concept: changing the shape of the tongue, lips, jaw, soft palate, and laryngeal height changes the acoustic “tuning” of the tract, which changes vowel clarity, brightness, warmth, and carrying power.
Resonance is not a separate “place” where sound goes. You may feel vibrations in the face, mouth, chest, or skull, but those sensations are side effects of sound energy interacting with tissues. The goal is not to chase sensations; it is to shape the tract so the sound is efficient, clear, and stylistically appropriate.
Vowels are resonance shapes
Each vowel corresponds to a specific vocal tract configuration. Small changes in tongue height and forward/back position can dramatically change resonance. For example, “ee” typically has a high, forward tongue and a narrower mouth opening, which can create a brighter, more focused sound. “ah” typically has a lower tongue and more open jaw, often sounding warmer and broader. When singers struggle with certain notes, it is often because the vowel shape is fighting the pitch: the tract is tuned in a way that makes the note harder to sustain without extra pressure.
Soft palate and nasality
The soft palate (velum) can lift to separate the oral and nasal cavities or lower to allow nasal resonance. In most classical and many contemporary singing contexts, vowels are primarily oral (soft palate lifted) with controlled, minimal nasal airflow. However, some styles use deliberate nasality for color. The key is choice: unintended nasality often comes from a soft palate that is not lifting consistently or from tongue tension that blocks the oral space.
Practical step-by-step: explore resonance shifts without pushing
Step 1: Hum on “mm.” Choose a comfortable mid-range pitch and hum lightly. Feel the buzz around the lips and face. Keep the jaw loose.
Step 2: Open to “mah.” From the hum, open into “mah” without changing pitch or volume. Try to keep the same ease and steady breath. Notice how the resonance “opens” as the mouth space increases.
Step 3: Alternate “mee-meh-mah-moh-moo.” Sing each vowel on the same pitch, medium-soft. Aim for consistent volume and ease. Observe which vowels feel tight or unstable; those are your “resonance challenge” shapes.
Step 4: Adjust one variable at a time. If “ee” feels tight, slightly relax the lips and allow a tiny bit more jaw drop while keeping the tongue forward. If “oo” feels muffled, allow a bit more inner mouth space (less lip rounding) while keeping the vowel recognizable.
How Airflow, Vibration, and Resonance Interact in Real Singing
Why “more breath” can make the sound worse
If you increase airflow without improving closure, the folds may be blown apart, producing breathiness and instability. The singer then often compensates by squeezing the throat, which increases collision forces and fatigue. Efficient singing usually uses less airflow than people expect, but with better timing and steadier pressure. Think “steady and economical,” not “big and windy.”
Why “more closure” can make the sound smaller
If you clamp the folds together too firmly, the vibration can become stiff. The tone may sound pressed, the pitch may feel stuck, and resonance may not “light up” because the source signal becomes less flexible. The goal is responsive closure that can adjust with pitch and vowel, not a fixed squeeze.
Resonance can reduce the need for effort
When resonance is well aligned with the pitch and vowel, the sound carries with less perceived effort. This is why two singers can sing the same note at the same measured loudness, but one feels easy and the other feels exhausting. The easy singer is often getting more acoustic efficiency from the vocal tract shape, not necessarily using more breath pressure.
Common Cause-and-Effect Patterns (Troubleshooting Map)
Breathy tone
Likely pattern: airflow leads, closure lags; pressure may be low or inconsistent.
What to try: slightly firmer consonants (like “v,” “z,” “m”), medium-soft volume, and shorter phrases to build coordination before extending.
Pressed/strained tone
Likely pattern: closure leads with excess pressure; throat muscles over-engage.
What to try: reduce volume, use gentle semi-occluded sounds (lip trill, “vvv,” “zzz”), and keep the vowel slightly narrower on higher pitches to avoid forcing the tract open.
Wobbly pitch or unstable sustain
Likely pattern: pressure fluctuates; resonance shape shifts unintentionally; onset is inconsistent.
What to try: 5-second steady holds on one pitch using “ng” (as in “sing”) then open to a vowel, keeping the same airflow feel.
Muffled or swallowed sound
Likely pattern: tongue retracts, jaw closes, or lips over-round; resonance space becomes overly dark.
What to try: slightly more forward tongue posture, clearer consonants, and a touch more mouth opening while keeping the throat relaxed.
Practical Lab: Build the Full Chain (Power → Source → Filter)
This short routine integrates airflow, vibration, and resonance in a controlled way. Use a comfortable pitch and stay at medium-soft volume. Repeat each step 2–3 times.
1) Power check: steady outflow
Step: Exhale on a quiet “sss” for 8 seconds.
Goal: even intensity from start to finish.
If you struggle: shorten to 5 seconds and build up gradually.
2) Source check: easy vibration
Step: Switch to “zzz” for 5 seconds at the same perceived breath effort.
Goal: a smooth, steady buzz without throat gripping.
Adjustment: if it feels tight, reduce volume; if it feels airy, slightly increase closure by making the “z” clearer.
3) Filter check: vowel clarity without extra push
Step: Move from “zzz” into “zah” (keep the “z” for a moment, then open to “ah”).
Goal: the vowel opens but the breath effort stays the same.
Adjustment: if “ah” gets loud and shouty, you likely increased pressure; repeat softer. If it gets dull, allow a bit more mouth space and keep the tongue relaxed.
4) Add pitch movement while keeping coordination
Step: On “zah,” sing a simple 1–3–5–3–1 pattern (do-re-mi-re-do) in a comfortable key.
Goal: same tone quality on each note, no sudden breath blasts, no jaw locking.
Adjustment: if the top note strains, narrow the vowel slightly (toward “uh/aw” depending on your voice) and reduce volume.
Mini Experiments: Hear the Difference Between Source and Filter
Experiment A: same source, different filter
Keep pitch and volume steady on a comfortable note. Sing “ee” for 2 seconds, then “ah” for 2 seconds, then “oo” for 2 seconds. Try not to change loudness. You will hear the tone color change mainly because the filter (vocal tract shape) changed, even though the source (fold vibration rate) stayed the same.
Experiment B: same filter, different source intensity
Choose one vowel, such as “ah.” Sing it softly for 2 seconds, then medium for 2 seconds, then softly again. Keep the mouth shape as consistent as possible. You will hear changes in intensity and possibly brightness because the source energy changed. If the medium gets harsh, you likely added too much pressure or too much closure; aim for a smaller increase in effort.
Key Terms You Can Use While Practicing
Airflow: the amount of air moving through the glottis and out of the mouth/nose.
Subglottal pressure: air pressure below the vocal folds that drives vibration.
Adduction: bringing the vocal folds together to resist airflow.
Glottis: the space between the vocal folds.
Onset: how the sound begins (breathy, hard, or balanced).
Resonance: how the vocal tract shapes and enhances the source sound.
Formants: frequency regions emphasized by the vocal tract shape that help define vowels and tone color.
Practice Notes: What to Monitor (and What to Ignore)
Monitor these
Steadiness: does the sound stay even, or does it surge and fade?
Ease at the onset: does the note begin cleanly without a gasp or a pop?
Vowel consistency: does the vowel stay recognizable as you change pitch?
Recovery: after a phrase, does your throat feel normal, or “worked”?
Ignore these traps
Chasing vibrations: facial buzz can be useful feedback, but it is not the goal.
Over-opening: a very dropped jaw or overly wide mouth can destabilize resonance and increase effort.
Forcing airflow: more air is not automatically better; coordination is better.
Quick self-check during a note: If you reduce volume slightly and the tone gets clearer, you were probably over-driving pressure. If you reduce volume and the tone disappears into air, you likely need a bit more closure or steadier pressure.
