Overtone singing, also called overtone chanting, harmonic singing, polyphonic overtone singing, or diphonic singing, is a singing method where a person creates two different pitches at the same time.

A basic note is produced by the human voice, and harmonic overtones can be made louder by changing the size and shape of the mouth and throat.

Overtone singing should not be confused with throat singing, even though some throat singing methods use overtone singing. While overtone singing requires careful control of the vocal tract, throat singing mainly focuses on the voice's source.

Asia

Overtone singing is believed to have originated in southwestern Mongolia, specifically in modern Khovd Province and the Govi Altai region. This style of singing is practiced throughout Mongolia and is often considered the most active area for overtone singing worldwide. The most common style, known as khöömii (Cyrillic: хөөмий), has several varieties:

• Uruulyn / labial khöömii
• Tagnain / palatal khöömii
• Khamryn / nasal khöömii
• Bagalzuuryn, khooloin / glottal, throat khöömii
• Tseejiin khondiin, khevliin / chest cavity, stomach khöömii
• Turlegt, khosmoljin khöömii / khöömii combined with long song

Mongolians also practice other singing styles, such as karkhiraa (meaning "growling") and isgeree.

In the Republic of Tuva, located in southern Siberia, Russia, overtone singing is also practiced. The Tuvan method of singing overtones focuses on sounds with many layers or textures. Tuvans have developed a wide range of rhythmic and melodic styles, most of which are sung using korekteer (meaning "with chest voice"). These styles include:

• Khöömei
• Sygyt
• Kargyraa (which also uses a second sound source made by false vocal folds called "false-folds-diplophony")

Other sub-styles include:

• Borbangnadyr
• Chylandyk
• Dumchuktaar
• Ezengileer
• Byrlang (a unique type of vibrato, mainly used in khöömei and kargyraa styles)

Traditionally, melodies are created using the 6th, 8th, 9th, 10th, 12th, 13th, and sometimes the 16th harmonics, which form the major pentatonic scale. The 7th and 11th harmonics are usually avoided.

A unique melody from Tuvan tradition is "Artii Sayir," often performed in the kargyraa style.

In neighboring Russian regions, such as the Altai Republic and Khakassia, forms of throat singing called kai (Altay: кай, qay) or khai (Khakas: хай, xay) are practiced. In Altai, this style is used for epic poetry, often accompanied by an instrument called a topshur. Altai narrators (kai-chi) perform in styles similar to those in Tuva, including kargyraa, khöömei, and sygyt. They also have their own style with very high harmonics, related to kargyraa. Variations of kai include:

• Karkyra
• Sybysky
• Homei
• Sygyt

The first well-known kai-chi was Alexei Kalkin.

The Chukchi people of the Chukchi Peninsula in northeastern Russia also practice throat singing.

Tibetan Buddhist chanting is a type of throat singing practiced mainly by monks in Tibet, including those in Qinghai Province, Nepal, Bhutan, India, and the Himalayan region. These chants often use the lowest possible pitches in throat singing. Ceremonies and prayers in Tibetan Buddhism frequently include throat singing, with multiple monks chanting at the same time. Styles include Gyuke (Standard Tibetan: རྒྱུད་སྐད་), which uses the lowest pitch; Dzoke (མཛོ་སྐད་); and Gyer (གྱེར་).

In Kazakhstan and the Uzbek region of Karakalpakstan, poet-musicians called zhirau use throat singing in their epic poetry, often accompanied by a dombra. Zhirau singers believe the ability to throat-sing is an innate gift given to certain Kazakhs and cannot be taught.

Another form of throat singing in Kazakhstan is "Kömeimen än aituw (Көмеймен ән айту)," which is similar to throat singing in the Altai Republic. This style is being revived by Kazakh ethno-folk bands HasSak and Turan Ensemble, as Kazakhs previously believed it had disappeared due to Russian conquest.

Balochi Nur Sur is an ancient form of overtone singing still practiced in parts of Pakistan, Iran, and Afghanistan, especially in the Sulaiman Mountains.

Dengbêj is a Kurdish-Yazidi style of bardic chanting that often includes overtones. This style is distinct from other forms of overtone singing. An article by Nick Hobbs titled "Dengbêj—Kurdish long song and overtone singing" (2020) discusses the use of overtones in dengbêj in detail. Dengbêj is a traditional style from Turkish Kurdistan, with practitioners mostly from Anatolia. While Kurdish folk songs are also sung, overtones are rarely heard outside of dengbêj.

Europe

On the island of Sardinia, Italy, especially in the Barbagia subregion, there are two styles of polyphonic singing. One style, called "singing a tenore," uses throat singing. The other style, called "cuncordu," does not use throat singing. Cantu a Tenore is performed by groups of four male singers, each with a different role. The 'oche or boche is the lead singer, while the mesu 'oche or mesu boche, contra, and bassu form the chorus. These roles are listed from highest to lowest pitch. The boche and mesu boche sing using their normal voice, while the contra and bassu sing using a special technique involving the false vocal folds, similar to methods used by Tuvan singers called Khoomei and Kargyraa. In 2005, UNESCO recognized cantu a tenore as an intangible world heritage. Well-known groups that perform this style come from towns such as Bitti, Orosei, Oniferi, and Neoneli. Each town usually has more than one group, and the group names often include the name of a specific place or monument and the town, such as "Tenore Su Remediu de Orosei."

The Sami people, who live in northern parts of Sweden, Norway, Finland, and the Kola Peninsula in Russia, have a singing style called yoik. While overtone techniques are not a main feature of yoik, some singers use them occasionally.

The Bashkirs of Bashkortostan, Russia, have a style of overtone singing called özläü (sometimes spelled uzlyau). This style is nearly lost. Bashkirs also sing uzlyau while playing the kurai flute, a traditional instrument. This technique of singing into a flute is also found in folk music in regions as far west as the Balkans and Hungary.

In Flamenco's Cante Jondo, singers sometimes use overtones at the end of phrases. This practice may have started as a way to make singing last longer and later became a valued musical feature. Singers like Carmen Linares and Duquende often use overtones in their performances.

Africa

Some Thembu Xhosa women in South Africa use a low, rhythmic way of singing with the throat, called umngqokolo. This style is similar to the Tuvan Kargyraa style. It often goes with call-and-response singing and complex patterns of rhythm.

Non-traditional styles

In the 1920s, a Texas singer named Arthur Miles created a style of overtone singing, similar to sygyt, to add to the yodeling in country western music. Blind Willie Johnson, also from Texas, is not a true overtone singer, according to National Geographic. However, his ability to shift from deep, guttural sounds to soft lullabies shows some similarities to the tones of overtone singing.

In the 1960s, some Western musicians worked with traditional throat singers or tried throat singing themselves. Some made new musical contributions. Since harmonics are found in all sounds, the idea of authenticity depends on the musical quality. Important musicians in this area include Collegium Vocale Köln (which started using this technique in 1968), Michael Vetter, Trần Quang Hải, David Hykes, Jill Purce, Jim Cole, Ry Cooder, Paul Pena (who mixed Tuvan throat singing with American blues), Steve Sklar, and Kiva (who focuses on jazz and world music and writes for overtone choirs). Others include composer Baird Hersey and his group Prana with Krishna Das (who uses overtone singing and Hindu mantras) and Canadian songwriter Nathan Rogers, who teaches Tuvan throat singing in Winnipeg.

Paul Pena was in the documentary Genghis Blues, which shows his journey to Tuva to compete in its throat-singing competition. The film won a documentary award at the 1999 Sundance Film Festival and was nominated for an Oscar in 2000.

Tuvan singer Sainkho Namtchylak worked with free jazz musicians like Evan Parker and Ned Rothenberg. Lester Bowie and Ornette Coleman worked with the Tenores di Bitti, and Eleanor Hovda wrote a piece using Xhosa singing. DJs and electronic musicians like the KLF combined their music with throat singing, overtone singing, or the theory of harmonics.

Trần Quang Hải, a researcher on overtone singing since 1969 in Paris, France, has written many articles and videos on overtone singing since 1971. His 1989 film The Song of Harmonics, directed by Hugo Zemp, won awards in Estonia, France, and Canada.

David Hykes started Harmonic Chant in New York in 1975, the same year he formed his group, the Harmonic Choir, which is considered one of the world’s top overtone ensembles.

Wolfgang Saus of Germany is a major teacher and performer of "polyphonic overtone singing." His skills make him easy to recognize. Trained as a classical baritone, he also composes and arranges polyphonic overtone music for solo voices and choirs.

A cappella singer Avi Kaplan used overtone singing during his group Pentatonix’s performances. He combined throat singing with a cappella dubstep.

The Overtone Choir Spektrum, from Prague, Czech Republic, is unique because it blends traditional choir singing with overtone techniques. It is the only one of its kind in the Czech Republic and one of the few in the world.

MuOM Ecstatic Voices is another unique overtone singing choir. It combines Western overtone singing with Tuvan and Mongolian throat singing styles (like kargyraa, khoomei, sygyt, ezengiler, and bonbarnadyr). Created in Barcelona in 2008, it has eight singers on average and specializes in creating overtone polyphony (each singer produces an overtone) and polyphony of the fundamentals, making two distinct sound layers.

Sherden Overtone Choir was founded in 2016 in Sardinia by Ilaria Orefice and Giovanni Bortoluzzi. The choir mixes Tuvan throat-singing styles with Sardinian throat-singing.

Contemporary multi-instrumentalist The Suitcase Junket uses a self-taught overtone singing or throat-singing technique.

Several classical composers have included overtone singing in their works. Karlheinz Stockhausen was one of the first, with Stimmung in 1968. Trần Quang Hải, a French-Vietnamese national, wrote "Về Nguồn" with Vietnamese composer Nguyễn Văn Tường in 1975. Australian composer Sarah Hopkins’s Past Life Melodies for SATB chorus also uses this technique. In Tan Dun’s Water Passion after St. Matthew, the soprano and bass soloists sing in various styles, including Mongolian overtone singing.

In 2014, German singer Anna-Maria Hefele became popular online with her "polyphonic overtone" singing. The Huffington Post praised her "amazing ability," calling her singing "utterly bizarre." On October 10, 2014, she was number two on The Guardian’s Viral Video Chart for her video Polyphonic Overtone Singing, where she demonstrates and explains overtones.

Istanbul-based British singer Nikolai Galen uses overtones in his experimental music. His solo album Emanuel Vigeland, the Black Paintings album Screams and Silence, and the Hoca Nasreddin album A Headful of Birds include these techniques.