
Overtone singing, also known as overtone chanting, harmonic singing or throat singing, is a type of singing in which the singer manipulates the
resonances (or
formants) created as air travels from the lungs, past the
vocal folds, and out of the lips to produce a
melody.
The
harmonics (fundamental and
overtones) of a sound wave made by the human voice can be selectively amplified by changing the shape of the
resonant cavities of the mouth,
larynx and
pharynx.
This resonant tuning allows singers to create apparently more than one
pitch at the same time (the fundamental and a selected overtone), while
actually generating only a single fundamental frequency with their vocal
folds (
links to samples below).
It is thought that the art of overtone singing originated from south western
Mongolia in today's
Khovd Province and
Govi Altai region. Overtone singing is a technique and cultural or spiritual musical
artform, developed in
Mongolia,
Southern Siberia,
Central Asia,
Tibet and in
South Africa. It also is used to a lesser degree in
Sardinia, the only ancient form of European overtone singing that is
still practiced. Many theories exist that overtone singing once had a
ritual and spiritual use in
Kabbalistic ceremonies,
Masonic lodges,
mystery schools and
Sufi practices.
There are videos on YouTube of an amazing artist,
Anna-Maria Hefele, performing
overtone singing with SUPERSONUS in several productions (
link below).
overtone graphic representations
Overview of glissando exercises based on the harmonic series.
Human proportion study by Albrecht Dürer (1471-1528).
The voice of overtone
singing is characterized by a sharp formant centered at nF0, as can be seen in
Figs. 1 and 2.
The
Kargyraa throat-singing style employs a characteristic low growling tone,
produced by other soft tissues in the vocal tract vibrating
sympathetically an octave below the frequency of the vocal folds.
This, among other things, gives the singer more harmonics to work with
in a given range of frequencies, for reasons that should become
somewhat clearer later on.
Performer Christian Zehnder exposes his singing to X-Rays. Image made
with the Dept. of Radiology at the CHUV Lausanne (link below). Extract from the
material of INLAND, a film by Pierre-Yves Borgeaud with Stimmhorn
(2002). Production: SF / SSR idée Suisse, momentum production.
Performer Christian Zehnder
The
low tone, or vocal subtone, is caused by the oscillation of tissues
that lie above the vocal folds. We use the vocal folds for everyday
speech and song. The tissues above these actual focal folds are known as
the false vocal folds, and you can see them on the diagram below, which
is a cross sectional view of the larynx.

When
the actual vocal folds are set into periodic vibration with a highly
tensed glottis, the false vocal folds are pushed together and slightly
upward toward the back of the throat. These slimy little flesh curtains
are set into motion to produce a subtone, they look and feel like
puckering lips.
When set into motion, these false
vocal folds vibrate most optimally, with maximum amplitude and
consistency, at exactly one half the rate of vibration of the actual
vocal folds. For example, if actual vocal folds are singing an A 440 Hz
and you set your false vocal folds into optimal vibration, you will
produce a strong subtone of 220 Hz simultaneously with the 440 Hz tone
of your actual vocal folds. Thus, producing two distinct oscillations
spaced one perfect octave apart.
Almost
any overtone-singing style is executed using one of three voices. The
“voices” are more than just three differing vocal timbres. The first
voice, the “neutral”or “natural”voice, uses no more laryngeal tension
than is necessary for speech. Second, the “throat” voice (known as the
khoomeivoice in
Tuva and neighboring regions in
Central Asia),
uses an immeasurable but clearly audible amount of increased tension in
the larynx. Technically, the throat voice is made by increasing the
length of the “closed phase” in each open-and-close cycle of a periodic
frequency. The throat voice is not unique to
Central Asia, and it can be heard in parts of Central and North Africa and among blues and rock vocalists such as
Howlin’ Wolf and
Captain Beefheart.
Third, there is the “subtone” voice, which I think of as a kind of
extension of the throat voice, but with prominent, and downright
unmissable, sympathetic vibration of the false vocal folds and, in many
singers, other surrounding tissues of the vocal tract.

The “voices”
Net links:
YouTube links: