Demetrio Stratos was born Efstratios Dimitriou in Alexandria, Egypt, on April 22, 1945, to Greek parents. He studied piano and accordion as a child and grew up hearing Byzantine church chant, traditional Arabic music and the first rock and roll. In 1957 the political upheaval in Egypt sent him to a Catholic college in Nicosia, Cyprus, where his family joined him two years later. In 1962 the family moved to Milan, and he enrolled in the architecture faculty of the Politecnico. He formed his first group there in 1963, began singing when the regular vocalist could not make a gig, and worked as a session keyboardist in Milan studios while his repertoire ran to soul, blues and rhythm and blues.

In 1967 he joined the beat band I Ribelli as keyboardist and singer, and the group's singles, among them "Pugni chiusi," made him a name in Italy. He left in 1970 and began the work that would define the rest of his life, an investigation of what a voice can do before it is trained into language. The starting point, he said, was watching his infant daughter Anastassia, born that year, play with sound in her first months of babbling. In 1971 he put out the single "Daddy's Dream" on Numero Uno, the label run by Mogol and Lucio Battisti. It was his last commercial pop record.

In 1972 he and the drummer Giulio Capiozzo founded Area in Milan, and the band's first album, Arbeit macht frei, appeared on Cramps Records in 1973. The founding lineup included the saxophonist Eddie Busnello and the bassist Patrick Djivas, both soon gone, and it settled around Patrizio Fariselli on keyboards, Paolo Tofani on guitar and synthesizer, and from 1974 Ares Tavolazzi on bass and trombone. Stratos sang and also played organ, steel drums and percussion, and Discogs credits him on harpsichord on the second and third albums. English Wikipedia describes Area as an Italian progressive rock and jazz fusion group, and the record catalogs reflect it: Discogs files Arbeit macht frei, Are(A)zione and their last album with him under jazz-rock. The band played about two hundred concerts in Italy in 1976 alone, and toured festivals in France, Portugal, Switzerland, Chile and Cuba.

The most openly jazz chapter of his career came in 1976. In Milan, Stratos, Fariselli and Tofani played a concert at the Aula Magna of the Università Statale with the American soprano saxophonist Steve Lacy and the English percussionist Paul Lytton, recorded on October 27 and issued by Cramps in 1979 as Event '76. Lacy and Lytton also joined Area on the studio album Maledetti (Maudits), whose central piece, "Caos," hands each player five cards naming a state (silence, irony, sex, violence, hypnosis) to improvise for a few minutes before drawing the next. In the same period he sang on "Amna," a track on La Cantata Rossa per Tall el Zaatar (1977), a record about the Tall al-Zaatar massacre led by the pianist Gaetano Liguori and the poet Giulio Stocchi.

Alongside Area he built a solo practice in extended vocal technique. Working with the phonetics researcher Franco Ferrero at the University of Padua, he showed that he could produce two, three and even four tones at once and reach frequencies near 7,000 Hz. The records of that work are Metrodora (1976) and Cantare la voce (1978), and neither is a jazz record in the ordinary sense. They belong to the avant-garde of the voice, and the circle around them was the Fluxus and John Cage world. Stratos recorded Cage's Sixty-Two Mesostics Re Merce Cunningham for solo voice, and in March 1978 Cage invited him to the Roundabout Theatre in New York for an Event staged by the Merce Cunningham Dance Company. That summer he took part in Cage's ten-hour broadcast in Amsterdam and in the three train rides of "Il Treno di John Cage."

He left Area after the 1978 album Gli dei se ne vanno, gli arrabbiati restano! to concentrate on voice research. In January 1979 he recorded Le Milleuna, a one-hour piece with a text by Nanni Balestrini, and he made a rock and roll record, Rock 'n' Roll Exhibition, with Mauro Pagani and Paolo Tofani. His last concert was a solo recital in Monza on March 30, 1979. In April he was diagnosed with aplastic anemia, was admitted to the Milan Polyclinic on April 2 and was taken to New York for treatment while he waited for a bone marrow transplant. He passed away there on June 13, 1979, aged 34. A benefit concert for his medical costs, set for the next day at the Arena in Milan, became his memorial, with some 60,000 people in the audience and over a hundred musicians on the bill. He is buried at Scipione Castello, near Salsomaggiore Terme, which began holding a memorial music festival in 2000. Since 2005 an international prize for experimental music has carried his name, and its career awards have gone to Diamanda Galás, Meredith Monk and Fred Frith, among others.

Stratos is best known as the voice of Italian progressive rock, and the jazz in his story is real but specific. In Area it was the improvising rhythm section, the metric and harmonic freedom of the writing, and a band that could open a concert to free improvisation with Steve Lacy and Paul Lytton. For his own vocal model, Italian sources point to the most advanced American Black-music singers, Leon Thomas among them, and he then went well past them into overtone singing, vocal traditions from the Mediterranean to Mongolia and Tibet, and the idea that a child's pre-verbal voice is the richest instrument there is. He treated voice as sound before it was language, and argued that exploring it was a form of psychological and political liberation as much as technique.

His solo albums are best heard as experimental vocal art rather than jazz, and he sits among the crossover artists for the Area records, the free-jazz sessions and the company he kept in Milan's improvising scene. Many critics and vocalists regard his extended techniques as an important step in what the voice can do on a record.