By Sam Jarman

The day dawns cold, clear, and still. A nomadic Mongolian herder knows that sound will carry well in these conditions, so he takes his chance. Climbing onto his horse, he rides into the wilderness, intent on finding a place where he can honour one of his people’s most sacred traditions. Using only his voice, he will imitate the song of birds, the hum of wind streaming over a rugged mountainside, and the hooves of wild galloping horses.

Finding the right spot is crucial. The herder needs to probe the nearby river valleys and mountaintops, to discover the place where his song will sound the most clearly.  If he chooses well, his voice could be heard for miles across the surrounding plains. He has learnt from his ancestors to use the Mongolian steppe as a sound studio; its open landscape providing the perfect acoustics to carry his voice. When he finds the right place, he begins his song.

His mesmerising chant often doesn’t sound like anything a human could create with their voice. The song could vary in pitch between being hauntingly deep, and as high as a flute. But astonishingly, he can sing both of these pitches, and many tones in between, at the same time.

For generations, people in Mongolia and surrounding areas in Siberia and northern China have learnt to use their voices to mimic the sounds of nature with a hypnotic accuracy. Even in the face of modernisation, the tradition remains as strong as ever today. It’s hardly surprising that the extraordinary talent of throat singing has become one of the most famous and iconic traditions in Mongolian culture.

Many Mongolians learn to throat sing from a very young age, but the techniques they use to produce such a bewildering array of sounds are anything but simple. To truly understand how they do it, we need to explore the anatomy of our own voices, and the physics of the acoustic waves we create with our vocal apparatus. Throat singers have learnt to intricately manipulate these acoustic waves to produce some astonishing sounds.

How it’s made: the human voice

Like any breath, or a normal speaking or singing voice, the song of a throat singer begins life as the lungs contract, forcing out a column of oxygenated air. The air travels upwards through the tube connecting our lungs to our throats, known as the trachea. But to distinguish the breath from a noiseless exhale, it first needs to pass through the larynx, sitting just above the trachea. The larynx contains a set of two vocal chords, which contract to a thin slit when we decide we have something to say, or rather sing.

Looking top-down: this little slit is responsible for every word you’ve ever said, even the embarrassing ones | Image: Henry Vandyke Carter

As air passes through the contracted vocal chords, they are forced to vibrate. These vibrations chop the air column up, forcing it to vibrate itself. At regular intervals, the air will be blocked entirely, and then be let through in a sudden rush. So, the air coming through the vocal chords vibrates in a pattern we are probably very familiar with: a sound wave.

The pitch, or frequency of these sound waves is ultimately decided by the size of our vocal chords. The tension in the chords, and the size of the gap between them, determine how much the sound waves they produce will vibrate over time. This gives them an important property, called the fundamental frequency – a value which entirely defines the unique pitch of each of our voices.

The fundamental frequency is heavily dependent on gender. Women’s vocal chords are usually smaller, meaning the air column in the trachea vibrates more over time, giving the sound waves a higher frequency. For men, larger chords will cause the air column to vibrate at a lower frequency. But the fact that no two voices sound the same can’t be explained by variations in pitch alone.

A sound wave in it’s purest form – you can see how air is compressed and spaced out at regular intervals. This type of wave is easy to understand, but lacks emotional depth… | Image: Pluke

On top of a fundamental primary wave in our voices, there are many smaller, higher-frequency waves also created by the vocal chords. Called overtones, each of these waves has a distinctive frequency; the first will have twice the frequency of the fundamental wave, the second will have three times the frequency, and so on. When stacked on top of each other, all of these waves create one intricate and complicated sound wave. This is the sound of our voices, as unique to each of us as our fingerprints.

 

…The sound waves of our speech are much more complicated

Already, these sound waves can accurately express our emotions. When listening to other people, our minds can tell if their voice indicates happiness, sadness, anger, or surprise, simply by picking up subtle patterns in its loudness and variations in frequency. But to turn the sound waves into a coherent language, the air finally passes through our mouths. The continuous movements of our throats, tongues, and lips sculpt sound waves into the words we use to communicate with each other (here’s a pretty hilarious demonstration of how it works).

We use our vocal apparatus so often that we don’t need to consciously think about how we need to manipulate it to produce the particular sounds we want. But for Mongolian throat singers, the anatomy we normally use to talk and sing has untapped potential. The secret of their captivating sound lies in an important phenomenon in acoustic physics, known as resonance.

Resonance: a perfect storm of sound

Every object in nature has a natural frequency it vibrates at. Normally, any vibrations the object interacts with won’t have the same frequency as its natural frequency. But if the two frequencies match up (with a few physical constraints), the object’s vibrations can become much larger. One of the most famous examples of resonance is the bizarre collapse of the Tacoma Narrows bridge in 1940:

The reasons why the Tacoma Narrows bridge acted so strangely before collapsing have been strongly debated, and still aren’t fully understood. But the most agreed-upon theory is that patterns in the strong winds blowing across the bridge that day had just the right frequency to induce resonance in the bridge, causing a huge standing wave to form in the it’s road. Eventually, the bridge’s suspension cables gave out, but not before giving an outlandish display of the properties of physics.

In the case of our vocal apparatus, the natural frequency is determined by the sizes of the gaps which the sound waves of our voices need to pass through. If the wavelength of the sound is equal to the size of the gap, the gap itself will be forced to vibrate, creating its own waves with the same frequency as the original sound. All of the waves add together in a ‘perfect storm’ to amplify the sound, making it much louder than it was originally – a resonant sound wave is formed.

Throat singers have learnt to manipulate parts of their vocal anatomy to produce resonant sound waves artificially. Different types of throat singing can cause resonance in different parts of the singer’s vocal apparatus. This creates a wide array of different types of throat singing, which each have their own name in the Mongolian language. The different styles are too numerous to cover in one article, but a smaller number of fundamental styles give rise to many of them.

Khoomei

In this style of throat singing, one or more of the smaller, higher-frequency overtone waves are caused to resonate as they pass through small, specifically-sized gaps in the singer’s throat and mouth. These waves are normally subtly engrained into our voices as individual overtones, but here, they can be heard as distinct, mesmerizingly clear sounds.

Astonishingly, the sound can be heard over the singer’s primary singing tone, meaning more than one note can be sung at a time by a single person. By the nature of our natural vocal sound waves, if we isolated all of the overtones which make up our voices, they would all be in harmony with one another. That means that the singer’s overtones create a one-person symphony without any further effort.

Typically in Khoomei, the singer will chant one continuous primary note, and then vary the overtones which are resonated. This creates a strong base sound, with a higher -pitched tune being sung above it. Mongolians believe the multiple tones of Khoomei give the impression of wind as it swirls around rocks and boulders, creating an enchanting natural chorus.

Sound: Alash Ensemble

Sygt

The highest of our natural overtones have far higher frequencies than anything a human could create with their natural voice. In this style, singers create a tiny gap between their tongues and teeth, to match the wavelengths of their highest-frequency overtones. The sound is shrill and piercing – as close as the human voice can come to sounding like a flute.

Like Khoomei, this style involves a steady fundamental tone being sung, with the resonant overtone above it. Yet in Sygt, the high-pitched overtone dominates the song; the gap which sound waves need to pass through is so small that the primary wave is greatly diminished. To Mongolians, Sygt is intended to mimic the sound of birdsong, and the warm, gentle summer breezes over the steppes.

Sound: Alash Ensemble

Kargyraa

Situated right above the vocal chords are two folds of membrane which look similar to the vocal chords, but normally serve an entirely different purpose. The ventricular folds are there to prevent food and drink from entering our airways, but throat singers have learnt to manipulate them to produce one of their most iconic sounds of all.

By manually contracting their larynx to exactly the right shape, throat singers can bring their ventricular folds and their vocal chords together. So when air passes through the vocal chords, the ventricular folds will resonate themselves, producing their own sound. However, this resonance is unlike the effects seen in other types of throat singing; here, the ventricular folds vibrate at exactly half the fundamental frequency, creating an artificial undertone.

In musical terms, halving the frequency of a sound will bring it down an entire octave. This has astonishing implications for throat singers. Kargyraa singers can reach a wide range of notes far deeper than anything they could sing using their vocal chords alone. The effect is a haunting, low-pitched sound, reminiscent of rolling thunder, or the mournful cries of a camel after losing her calf.

Sound: Alash Ensemble

Kargyraa in particular can partly explain why throat singing still remains so popular in Mongolia today, and is even facing a resurgence. In the past, social taboos meant that women weren’t allowed to practice the tradition, but now, these barriers are breaking down. Female vocal chords may be smaller, but women can still contract their ventricular folds to create a fantastically deep sound:

Now that men and women have equal opportunities to practice the art, throat singing is being taught to boys and girls across Mongolia and the surrounding regions; all eager to pass on the traditions of their ancestors. The iconic sound has made its way into concert halls and recording studios, and in the West, throat singing has gone from a mysterious, alien practice, to one which is beginning to influence our own culture.

Anatomically, there is no special adaptation among the Mongolian people that enables them to throat sing better than anyone else. It’s no easy talent to learn, but we are all capable of recreating the effects of resonance on our voices, if we practice for long enough.

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