The Larynx: True Folds, False Folds, Cartilages

The larynx is a box of cartilage at the top of the trachea. The big shield-shaped thyroid cartilage makes the 'Adam's apple'. Below it sits the ring-shaped cricoid; on the cricoid's back rim sit two small pyramid-shaped arytenoid cartilages that can rock and slide. The vocal folds stretch from the inside of the thyroid (front) to the arytenoids (back). The whole assembly hangs from the hyoid bone, which floats freely and is tied by muscles to the tongue, the jaw and the sternum.

Four groups of muscles do the work. The cricothyroid tilts the thyroid forward over the cricoid and so stretches and thins the folds — it raises pitch. The thyroarytenoid (vocalis) is the body of the fold; it shortens and thickens it — chest quality. The lateral cricoarytenoid and the interarytenoid bring the arytenoids together and so close the glottis; the posterior cricoarytenoid is the only muscle that opens it (for breathing). A good singer balances all of them from note to note.

Above the true folds lies a small pocket, the ventricle of Morgagni, and above it a second pair of folds: the false vocal folds, or vestibular folds. They are thick mucosal folds with few muscle fibres and normally do not vibrate. Their job is protective: they slam shut when we swallow, cough or strain (lifting a weight), keeping food out of the airway and fixing the chest. In ordinary singing they should be retracted so the true folds are visible from above. If the singer squeezes the supraglottic larynx — typically when pushing for volume or when the larynx is too high — the false folds move toward the midline and over the true folds. The sound becomes hoarse, 'held back' and effortful, the pitch may sag, and the voice tires fast. Some styles use them deliberately (growl, kargyraa in Tuvan throat-singing, rock distortion), where they vibrate together with or instead of the true folds, usually at a lower pitch.

The epiglottis is a leaf-shaped cartilage that folds over the larynx when we swallow. The tube between the folds and the epiglottis (about 2 cm) is the epilaryngeal tube. Narrowing it relative to the throat above it creates an extra resonance that boosts the third to fifth formants — the 'singer's formant' near 3 kHz. The tube narrows safely when the singer adopts a cry-like or startled quality (a restrained 'whimper') — not when the supraglottic muscles clamp down. The difference between a helpful narrowing and a harmful squeeze is largely one of effort and onset: easy, flow-like phonation is healthy, a hard bang is not.