In 2019, Kim Hyuk Gun (김혁건), the vocalist of THE CROSS (더크로스), showed the organs that move the breath in his doctoral dissertation through photographs he took of a human anatomical model. The dissertation gives the reason: the model makes it possible to look three-dimensionally at the body's organs involved in phonation, especially the work of the diaphragm and the breathing muscles.
This is the fourth part of the series. It sets out the structure and workings of the lungs, the diaphragm and the breathing muscles that lie beneath the three kinds of breath in Part 3.
01.The Breath for Resting and the Breath for Sound
The dissertation divides breathing into two kinds.
| Breathing at rest | Breathing for phonation | |
|---|---|---|
| Purpose | Keeping the body alive — gas exchange must be sufficient | Producing vocal energy and gas exchange happen together |
| Inhale | Activity of the inspiratory muscles | Short and quick |
| Exhale | Happens passively, through the elasticity of the lungs, the weight of the rib cage and the relaxing of the diaphragm | Controlled and slow |
Breathing is a bodily function that happens automatically, but the dissertation explains that breathing must be controlled for phonation, and that this is a complex function that has to be learned from infancy. It also writes that the steadiness and control of the inhale and exhale directly affect phonation: the overall quality and intelligibility of the voice differ depending on the basic level of breathing and on whether a steady inhale and exhale can be kept up during phonation.
02.Breathe In Short, Let It Out Slowly
The breath for speaking or singing is different from the breath for resting. The dissertation explains that when people make sound they have "an extremely short inhalation compared with the exhalation." They take in air quickly in that short time, then let it out slowly while controlling it, making sound naturally.
The dissertation also traces how this breath develops. After birth, people begin breathing with the diaphragm; as they grow, the muscles around the neck develop, a space forms between the shoulders and the neck, and the rib cage gradually lowers and widens. That is how people become able to regulate a full inhale and exhale appropriately during phonation. As needed, they let out a measured amount of breath to vibrate their vocal folds, and then the articulators move to produce the sound.
As the basis for developing breathing patterns, the dissertation names the inner muscles of the rib cage, the abdominal muscles, and the rib cage's size, stability, symmetry and movement.
03.The Lungs: A Sponge That Cannot Move on Its Own
The breathing organs include the nose and pharynx, the larynx, the bronchi and lungs, the diaphragm and rib muscles, and the abdominal wall muscles, and they work closely together to help breathing happen. The dissertation opens them up one by one on a human anatomical model.
The lungs are the main breathing organ, but they cannot contract or expand on their own. The dissertation compares the lungs to a pair of elastic sponges. They supply fresh air to the blood and send stale air out, but although they are elastic, they cannot draw in air by themselves, nor push air out for singing.
The process of air entering the lungs is called pulmonary ventilation, and it happens through "bulk flow," a large volume of air moving at once. Bulk flow moves because of the pressure difference between the two ends of the air passage.
| Pressure inside the lungs | Air | |
|---|---|---|
| Inhale | Falls below atmospheric pressure | Comes in |
| Exhale | Rises above atmospheric pressure | Goes out |
The anatomical model shows, in turn, the heart surrounded by the lungs with the diaphragm and liver below; the ribs joined to the spine once the organs are removed; and, with the ribs and lungs removed as well, the larynx, the esophagus and the airway leading to the lungs.
04.The Diaphragm: The Floor Between Chest and Belly
The diaphragm plays an essential role in making the inhale possible, and it also works importantly in the exhale. The dissertation calls it "the ceiling of the abdomen" or "the floor of the chest," and describes it as tendinous tissue lying crosswise between the lungs, the internal organs and the heart. It rises upward in a dome, with the right side of the dome a little higher than the left — a double dome. Above it sit the lungs and heart; below it, the rest of the internal organs.
The way breath goes out is like a balloon. When the inhale ends, the nerves that were stimulating the inspiratory muscles stop, the muscles relax, and the lungs return to their original volume. The dissertation calls this "passive elastic recoil," and calls the air in the lungs going out through the airway at this moment "passive expiration."
| Kind of exhale | When | How |
|---|---|---|
| Passive expiration | At rest | Without using muscles, through the elastic recoil of the lungs. Even early in the exhale, though, some inspiratory muscles stay contracted so breathing continues rhythmically and smoothly |
| Voluntary / active expiration | During exercise that calls for a lot of breathing | The expiratory muscles contract and push the exhale out actively |
05.The Muscles That Bring Breath In and Send It Out
On the inhale, the muscles attached to the rib cage and the diaphragm contract, so the volume inside the chest grows and the pressure drops, and air comes into the lungs. The dissertation writes that among them the diaphragm is the most important muscle. At rest, the diaphragm accounts for 60–70% of the volume inside the chest, and the rib cage for the rest.
| Muscle | What it does | |
|---|---|---|
| Center of the inhale | Diaphragm | Contracts to increase the chest's top-to-bottom diameter |
| Helping the inhale | External intercostals | Pull the ribs outward and up to increase the front-to-back diameter; their main work is in deep breathing rather than quiet breathing |
| Accessory inhale | Scalenes, sternocleidomastoid, pectoralis minor, trapezius, pectoralis major | Do almost nothing at rest; during exercise or a deliberate strong inhale they lift the collarbones and upper ribs and steady the diaphragm's movement |
| Exhale (at rest) | None | Passive, through the elasticity of the rib cage and lungs |
| Exhale (voluntary hyperventilation, exercise) | Abdominal wall muscles such as the internal obliques and rectus abdominis | When they contract, the diaphragm rises and the ribs are pulled down and inward, raising the pressure in the lungs |
| Forced exhale | Internal intercostals (prime movers); rectus abdominis, transversus abdominis, obliques (assisting) | Move the ribs in and down and raise abdominal pressure to push the diaphragm up |
The rib cage is also an important part of breathing. It is a cylinder made of the spine, the ribs and the breastbone, narrow at the top and wide at the bottom. Because the ribs are joined to the spine by joints, they can move up and down, and that movement changes the volume of the cylinder.
The "accessory inhale" row of the table connects to the problem of chest breathing in Part 3. The dissertation writes that during a strong inhale these accessory muscles lift the collarbones and upper ribs.
06.Today's Practice
Turned into points to check while you practice, what the dissertation and the lesson highlight looks like this.
- Breathe in short, let it out slowly — Breathe in quickly, then let that breath out slowly while controlling it (section 02; dissertation p.71).
- Do your collarbones lift on the inhale? — Lifting the collarbones and upper ribs on a strong inhale is the work of the accessory muscles (section 05; dissertation p.80). Check whether your collarbones and shoulders rise on the inhale while singing (Part 3; dissertation p.67).
- Breathe in through the nose; keep the shoulders and chest still — Lesson Ep. 6 (Chest-Voice Technique) gives breathing in through the nose and keeping the shoulders and chest still as the first two steps of chest-voice singing (video description).
The lesson to watch with this part is Season 1, Episode 6, "Chest-Voice Technique." Its description lists four steps of chest-voice singing: breathe in through the nose, keep the shoulders and chest still, the tongue root and soft palate, and gathering the mouth. The first two steps are the breath of this part; the tongue root and soft palate continue in Part 12 · Chest Voice.
07.Where to Go Next
The differences among the three kinds of breath are in Part 3 · Chest, Rib and Abdominal Breathing, and the larynx and vocal folds that turn breath into sound continue in Part 5 · The Larynx and Vocal Folds. A song sung with a breath taken in short and controlled long can be heard in THE CROSS's "Don't Cry". Lesson videos are in Korean.
The lungs cannot move on their own — and that is why breath becomes something you can practice.