The Flute in the Throat - What Acoustics Has Not Yet Explained

You have heard an overtone singer produce a clear harmonic, almost supernatural, floating above the drone like a crystal whistle. A sound that seems too pure to come from a human body. Too precise. Too bright.

Researchers in vocal acoustics have measured it, analyzed it, modeled it. And yet, something resists. The classical equations do not fully explain why this harmonic is so narrow, so intense, so stable.

It is from this mystery that a hypothesis was born, which I published in December 2025 on the scientific platform Zenodo: Here is a lively translation of what it proposes.

The Acoustic Paradox of Overtone Singing

In overtone singing, particularly in the sygyt style, the singer produces a harmonic of disconcerting purity. On a vocal spectrogram, this resonance draws a thin, bright line, isolated from the rest of the spectrum like a star in a dark sky.

Researchers who measured this resonance noticed something strange: it is more precise, more intense, more stable than the soft cavities of the vocal tract should normally allow. The mouth, the pharynx, the tissues (these spaces made of flesh and air) naturally dampen sound. They round the edges. They are not supposed to produce such a sharp resonance.

And yet, the overtone singer does it.

According to classical acoustic models, this level of precision should not exist. Something else is happening, something these models do not yet explain.

A Flute in Tune with the Voice

The idea of a “flute in the throat” may seem metaphorical.

And yet.

In the 1970s, Demetrio Stratos explored what he called flautofonia: flute-like sounds obtained by resonance in the cavities of the vocal tract, sometimes without vibration of the vocal folds. He showed that the voice could, under certain conditions, transform into a true wind instrument. In other words: a flute in the throat could replace the voice.

What I propose here is of a different nature.

What if an analogous mechanism, a fine coupling between airflow and resonance, could emerge without interrupting the sung voice? Not a flute that replaces the vocal folds, but a “flute” that synchronizes with them.

Not a replacement. An accord.

From this perspective, the breath would not produce an independent sound. It would come to stabilize an already present harmonic, as if the airflow and the cavity recognized each other, a subtle lock-in that would reinforce the resonance where soft tissues would normally have stifled it.

The Hypothesis in Three Components

1. A Hidden Cavity Between the Tongue and the Palate

When an overtone singer lightly touches the hard palate with the tip of the tongue, they create a well-known configuration, a double cavity that allows formant convergence. This, acoustic research has long documented.

What the hypothesis identifies as new is what happens above the back of the tongue: a cup-shaped cavity, bounded by the concave surface of the tongue and the palate, closed on the sides by a U-shaped contact between the lateral edges of the tongue and the dental arch. This cavity has openings between the upper and lower molars, where the edge of the tongue slightly parts, and that is where, according to the hypothesis, the decisive element resides.

It is not this cavity that chooses the harmonic. The selection is already ensured by formant convergence, as existing research has well established. What this cavity would do is something else: amplify the already selected harmonic thanks to its own resonance frequency, and actively attenuate its neighbors via anti-resonances generated by the lateral channels. Not a selector, a dual-action booster.

It is this combination (gain on the target, suppression of neighbors) that could explain the 35 to 65 decibels of attenuation of adjacent harmonics that researchers have measured, and which passive models struggle to justify.

2. The Breath That Makes the Cavity Sing

A transverse flute sings because the breath, projected against the bevel of the embouchure, creates small vortices of air. These vortices synchronize with the resonance of the tube, and from this synchronization the sound is born, sustained and amplified.

The hypothesis proposes that something analogous occurs at the inter-molar openings of the overtone singer. The airflow passing through these narrow spaces could create similar vortices. And if these vortices reach the natural frequency of the supra-lingual cavity, a coupling sets in: the system ceases to simply filter the sound, it injects energy into the resonance, compensating for the losses that soft tissues would normally cause.

It is this mechanism (regenerative and non-linear) that would explain the abnormal purity of the harmonic. And why the flute is an apt metaphor: not because the throat resembles a tube, but because the same physical laws could be at work there.

3. Why It Can Be Learned - But Takes Time

For this accord to establish itself, three families of parameters must converge: the opening of the lips, the constriction between the back of the tongue and the uvula, and the geometry of the lateral spaces between the molars. What is remarkable, and pedagogically important, is that these three parameters all work in the same direction: the more one of them opens, the higher the harmonic rises. There is no contradictory signal.

This makes the system learnable. But not simple for all that.

Beginners generally find the harmonic through the lips, an accessible but coarse control. Intermediate singers refine it through the linguo-uvular constriction. Experts learn to control the lateral geometry, structures that no one has shown them, that the mirror does not reveal, and that are part of no ordinary speech gesture. It is perhaps this that the Tuvan masters spent years discovering, without ever being able to quite explain it.

The harmonic is not placed. It happens, when the right conditions are met, all at once.

What This Changes for Learning

If this mechanism is real, it invites a shift in posture in learning.

Rather than seeking the right position, it is about seeking the right state, a moment where several fine adjustments converge toward something that triggers almost by itself. What I sometimes call, in my workshops, seeking balance, not position.

This demands patience, very fine listening, and a tolerance for wandering. Paradoxically, less muscular effort than one imagines. When the accord occurs, one recognizes it precisely because something ceases to force.

An Open Hypothesis

This work was deposited in open access on Zenodo in December 2025:

Psallidakos, I. (2025). Flute in the Throat: A Vortex-Acoustic Lock-In Hypothesis for Overtone Singing. https://zenodo.org/records/18868408

It generates predictions that specialized research teams can test, notably through coronal or axial imaging, or fine analysis of airflow at the inter-molar spaces. If you are a researcher in these fields and this path interests you, contact me. I would be happy to exchange.

And if you are a singer, practitioner, or simply curious — come experiment with this research from the inside, during a workshop or overtone singing training.

The best way to understand a resonance is still to feel it.

An obstacle can disturb, or make sing. The flute knows. The singer learns.

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By Iannis Psallidakos — overtone singing teacher & vocal acoustics researcher. About →