In 2019, Kim Hyuk Gun (김혁건), the vocalist of THE CROSS (더크로스), gave one section of his doctoral dissertation the title "The balance of force between the vocal folds and the diaphragm." Its first point is: "You must find the balance of force between the vocal folds and the diaphragm without forcing the belly."
This is the sixth part of the series. It brings together once more the larynx and vocal folds seen in Part 5, and sets out how breath and vocal folds should share the force on high notes.
01.Folds Above the Folds: True and False Vocal Folds
The dissertation sums up the human vocal organs as the vocal folds and laryngeal muscles that make sound directly, together with the glottis. Looking down at the larynx from above, there are the vocal folds (true vocal folds), made of two bands of membrane, and above them the false vocal folds, similar in shape.
| Structure | Where | What it does |
|---|---|---|
| True vocal folds | The two lower bands of membrane | Vibrate as the exhale passes, making the voice |
| False vocal folds | Above the true vocal folds | Similar in shape to the true vocal folds |
| Ventricle of Morgagni | The deep hollows on the left and right between the false and true folds | Contains tissue that secretes mucus, keeping the folds moist so they vibrate easily |
| Epiglottis | Above the vocal folds, between the larynx and pharynx | A ladle-shaped cartilage that closes or opens the passages to the windpipe and esophagus |
The dissertation sees the ventricle of Morgagni and the true vocal folds as the core of the vocal organs. The laryngeal muscles include the intrinsic group, which plays the leading role in phonation, and the extrinsic group, which assists it. How the true and false folds are used continues in Part 7 · Chest (Full) Voice and Part 8 · Falsetto and Registers.
02.The Glottis Takes a Different Shape for Breathing and for Sound
The glottis, the gateway of the larynx, is made of a pair of vocal folds. The dissertation explains the glottis like this.
| Shape of the glottis | |
|---|---|
| When breathing | The upper part of the true vocal folds opens wide into a triangle |
| When making sound | The left and right true vocal folds come together and meet at the midline |
The space between the two true vocal folds is called the membranous glottis and the space between the arytenoid cartilages the cartilaginous glottis; together they are called the glottis. The glottis tenses and contracts with the pressure difference created by the air coming from the lungs, adjusting the width of the passage — and that is what makes vocal sound possible.
With the larynx removed on its own, you can see the vocal folds and the Adam's apple — the thyroid cartilage. The passage containing the vocal folds is the airway, and the passage behind it is the esophagus. A footnote in the dissertation adds that the thyroid cartilage is the largest cartilage of the larynx with the vocal folds inside it, and that men's glottis is longer, giving a thicker, lower voice. The vocal folds in the airway can regulate the amount, strength and pressure of the breath.
03.Do Not Force the Belly
The dissertation writes that what matters in phonation is balancing the force and the action among the organs. One of these is the balance between the diaphragm and the vocal folds.
If the exhale has to get stronger for high notes, should you push your belly as hard as you can? The dissertation's answer is no. The higher the note, the more the vocal folds narrow to send the breath out far and strong, and the diaphragm rises to push the exhale out more strongly. But when abdominal pressure is too strong and the exhale too forceful, too much force goes into the vocal folds as they narrow the glottis to take that breath. In that case, the force is redistributed by lowering the diaphragm so the vocal folds can release some of it.
04.Low Notes and High Notes: The Glottis Changes Shape
The dissertation explains that the glottis changes with pitch.
| Low notes | High notes | |
|---|---|---|
| Glottis | Shorter and wider | Longer and narrower |
| Vocal-fold vibrations | Fewer | More |
| Exhale | — | Sent out far and strong |
| Diaphragm | — | Rises to push the exhale out more strongly |
| Where it resonates | Lower | Higher |
The dissertation's comparison is a garden hose. Just as water shoots far and strong when you pinch the end of a hose, on high notes the breath goes out far and strong as the vocal folds narrow. Head voice, the dissertation explains, is the sound made when the folds have narrowed and strong abdominal pressure sends the exhale up to resonate higher in the spaces of the head; the higher the note, the higher the place of resonance — that is the principle of resonance. Resonance continues in Part 9.
05.Three Principles for High Notes
The dissertation sets out three principles for singing high notes.
- Use abdominal pressure.
- Do not narrow the airway by tensing the external muscles of the neck. Instead, narrow the glottis by lengthening the vocal folds with the cricothyroid muscle. When the airway narrows, the path of the exhale narrows and the sound turns muffled (the dissertation warns against becoming "인골라" — in-gola, which a footnote in the dissertation explains as "the larynx (gola) sinking in (in)," that is, a sound with force caught in the throat).
- Train the vocal folds and the diaphragm together. Without enough strength training of the vocal folds and the diaphragm for high notes, voice breaks can occur. Steady high notes need strong muscles in both the vocal folds and the diaphragm.
In short, the force of a high note comes neither from the belly alone nor from the throat alone. The belly pushes the breath, and the vocal folds take that breath long and narrow. The cricothyroid is the muscle in the table in section 03 of Part 5 that "works when raising the pitch."
06.A Voice Break Is a Sign the Balance Has Broken
This principle also lines up with the results of the dissertation's experiment. In the experiment in which the belly was pressed to make the participants exhale, the dissertation reported that when the exhaling force was too strong and the force closing the vocal folds was too weak, the forces fell out of balance and the note broke (Part 1, section 06).
When a high note flips in the practice room, pushing the breath harder will not fix it on its own. Is the breath overpowering the vocal folds, and are the vocal folds ready to take the breath? You have to look at both sides together.
07.Today's Practice
Turned into points to check while you practice, what the dissertation and the lesson highlight looks like this.
- The outside muscles of the neck — On high notes, check that no force goes into the muscles at the front and sides of your neck (principle 2 in section 05 — do not narrow the airway with the external muscles; dissertation p.92). Lesson Season 2 Ep. 7 (Releasing Throat Tension) also explains sharing the force among lowering the diaphragm, the force that brings the vocal folds together, and nasal resonance (video description).
- Take force off the belly — If force piles up on the vocal folds on high notes, instead of squeezing the belly harder, redistribute the balance by lowering the diaphragm so the vocal folds can release that force (section 03; dissertation p.92).
- Mark your voice breaks — Next to the range you noted in Part 1, write down the note where your voice flips, and mark it as the place where the balance between your vocal folds and diaphragm needs to be found again (section 06; dissertation p.92, principle 3). Part 17 · Passaggio covers how to cross this zone.
The lesson to watch with this part is Season 2, Episode 7, "Releasing Throat Tension." Its description lists sharing the force among lowering the diaphragm, the force that brings the vocal folds together and nasal resonance; ring-shaped (circular) breathing; and the cricothyroid. Ring-shaped breathing is covered in Part 19 · Posture and Correct Breathing, together with the dissertation's figure "Types of abdominal breathing."
08.Where to Go Next
The structure of the vocal folds and how sound is made are in Part 5 · The Larynx and Vocal Folds, and the sound made with the folds together continues in Part 7 · Chest (Full) Voice. The high notes sung again with this balance can be heard in THE CROSS on Sugar Man 3: "Don't Cry" and "For You". Lesson videos are in Korean.
The belly pushes the breath, and the vocal folds take it — a high note comes not when one of them wins, but when the two hold against each other.