How a Voice Is Made: the Whole Chain

Almost every question about singing technique can be answered with one model: the source–filter chain. The lungs and the breathing muscles are the power supply; the vocal folds in the larynx are the sound source; the throat, mouth and (optionally) nose are the filter that shapes the raw buzz into a vowel; and the lips radiate the result into the room. The four stages are physically separate, but they are linked by muscles and bone — so a problem at one stage usually shows up as a compensation at another.

The source is not a string. The vocal folds are two small folds of muscle and mucosa that are blown apart by air pressure from below and pulled together again by elastic recoil and a drop in pressure between them (the Bernoulli effect). Each opening and closing releases a puff of air; hundreds of puffs per second blend into a tone whose pitch is the rate of vibration (about 100 Hz for a low male voice, 1000 Hz for a high soprano). The raw buzz contains the fundamental and a long series of harmonics, falling in strength by about 12 dB per octave.

The filter changes which harmonics are loud. The tube from the folds to the lips is about 17 cm long in an adult man (about 14–15 cm in a woman). It resonates at certain frequencies called formants; harmonics close to a formant are boosted and the others are weakened. Moving the tongue, jaw, lips and larynx changes the shape and length of the tube and therefore the formants: that is how a vowel 'ee' differs from 'ah', and how a singer's tone can sound dark, bright, pinched or full without changing pitch.

A practical consequence: you can't judge technique by sound alone. The same sound can come from different muscle patterns, and the same pattern can sound different on different vowels or pitches. The Voice Lab therefore combines three things — an anatomical model, measurements from your own recording, and sensations you can check with a mirror and your fingers — and treats each as evidence, not as proof.