The Vocoder: The Incredible History of a Great Invention

How the speech and voice changer was first implemented in the military, later used in science-fiction films, and eventually had its triumphant return in pop music.

Der Vocoder V256Deutsches Museum

The Vocoder

Known from music and the world of rock and pop, many musicians have used it to great effect as a voice changer over the last few decades, and it's still used in numerous films to this day: the vocoder. Still, what many people might not know is that the vocoder didn't start in the entertainment industry at all. It was actually the result of military research…

Der Sprechapparat von Kempelen (1771)Deutsches Museum

We need to go far back into the past to reach the beginning of artificial voice creation. Scientists have experimented with producing speech synthesis long before the invention of electronics. Around the turn of the first millennium, a certain Gerbert of Aurillac is said to have created a bronze-plated talking head that was even able to say yes and no.

Later, around 1800, a device emerged that was the first of its kind, and which is now based in the Deutsches Museum: Wolfgang von Kempelen's speaking machine.

Wolfgang von Kempelen (1734–1804) gained a great deal of attention with his book Mechanismus der menschlichen Sprache (Mechanism of human speech). At over 450 pages, it covers the origins of language, its sounds and the human speech mechanism. Halfway through the book is a chapter on the talking machine in which he describes his research and different machines. At the end he describes his latest experiment in detail through multiple to-scale illustrations, with the intent of allowing readers to rebuild and further develop it. Whether von Kempelen was the one who actually built the talking device is still up for debate.

Video zum SprechautomatDeutsches Museum

This replica shows just what the talking device is able to do…

Unumstritten ist, dass Homer Dudley (1896 – 1980) als Erfinder des Vocoders gilt. Der Priestersohn aus Virginia hatte sich beim Studium an der Penn State University mit der Wissenschaft der Elektrotechnik beschäftigt. Dudley fand schließlich Arbeit bei den Bell Laboratories in Murray Hill, New Jersey. 1928 begann er mit der Entwicklung eines Geräts, das den Klang der menschlichen Stimme in seine Bestandteile zerlegen und synthetisch wiedergeben konnte.

Das Schema eines Vocoders (1940)Original Source: Homer Dudley (October 1940). "The Carrier Nature of Speech". Bell System Technical Journal, XIX(4);495-515. -- Fig.8 Schematic circuit of the voder.jpg: Internet Archive Book Imagesderivative work: User:Clusternote / CC BY-SA (

The key to this invention were the filters. These could filter out certain areas of the acoustic spectrum which were above or below a specified frequency. Buzz produced vocals and vocalized consonants, and hiss non-vocalized consonants and sibilants. Only voice components that were just barely sufficient for communication could ultimately be heard. Its great advantage was that, by reducing the frequency of the voice to a required minimum, conversations could easily be transported over longer distances.

Voder-Präsentation (1939)Deutsches Museum

Dudley's presentation on the Voder, a further development on the vocoder, created quite the stir at the 1939 New York's World Fair. The principle was similar. Only the input signal was not the human voice. Instead, a woman named Helen Harper operated a keyboard and pedals, like an organ, which the voder then converted into an artificial human voice.

Voder-Werbeplakat (1940)Deutsches Museum

What the auditorium in New York could hear, for example, was the phrase "Good afternoon, Radio Science." According to the New York Times, however, the quality was so astoundingly poor that it sounded like something otherworldly had spoken underwater.

Gen. Eisenhower (Us Army & Signal Corps)LIFE Photo Collection

Naturally, the military (pictured here: General Dwight D. Eisenhower was also keen to hear about it. With the vocoder as their basis, Bell Labs developed the SIGSALY system, a hefty machine weighing over 50 tonnes for speech encryption which politicians and the Allied militaries could use to communicate across the Atlantic. It encrypted the voices of the speakers at one end of the line every 20 milliseconds—50 times per second—and sent them across the Atlantic. The voices were only decrypted and synthetically reconstructed for the listener once they reached the other end.

By George SkaddingLIFE Photo Collection

12 of these huge terminals were set up worldwide—the first in the Pentagon in Washington…

…the second almost 200 feet below Selfridges shopping center on Oxford Street, right next to the US embassy on Grosvenor Square…

By Bob LandryLIFE Photo Collection

…and another later in 10 Downing Street, the home of the British prime minister.

Winston Churchill (1951) by Alfred EisenstaedtLIFE Photo Collection

Winston Churchill and…

Roosevelt (1944-11-19) by George SkaddingLIFE Photo Collection

Franklin D. Roosevelt contacted each other so often that after being commissioned in 1943, SIGSALY enabled them to have around 3,000 telephone conferences before the end of the war.

The vocoder became less significant after 1945 up to the beginning of the 1960s. It therefore gained popularity in a totally different field: the entertainment industry.

Das Siemens-Studio für elektronische Musik by Alexander Schaaf und Helmut KleinDeutsches Museum

In the entertainment industry. Werner Meyer-Eppler, founder of the Studio for Electronic Music of the West German Radio, had already investigated synthetic language in 1948 in his book Electronic Sound Creation (Elektronische Klangerzeugung).

From 1956 to 1959 a vocoder was integrated in the Siemens Studio, now a Deutsches Museum exhibit, which was used among other things to record the legendary countdown of cult sci-fi series Orion Space Patrol (Raumpatrouille Orion) in the 1960s.

2001: A Space Odyssey (1968) by Dmitri KesselLIFE Photo Collection

Writers and directors at the time in general liked to use vocoders for science-fiction films in particular. For example, Stanley Kubrick used one for an unforgettable scene of his space epic 2001: A Space Odyssey when he made the HAL 900 onboard computer sing the song Daisy Bell.

2001: A Space Odyssey (1968) by Dmitri KesselLIFE Photo Collection

For background, according to lore, co-author Author C. Clarke happened to attend a synth vocoder presentation at Bell Labs and was deeply impressed when the IBM 704 sang the song Daisy Bell.

Autobahn (1954-03-24) by Ralph CraneLIFE Photo Collection

The world of distorted and alien voices became even more popular from the 1970s. As the greatest pioneers of electronic music, Kraftwerk used the vocoder more and more often, such as in their epochal album Autobahn in 1974 where they formed their unemotional, cold, industrial-electro sound that was typical for them from this point onward.

Bruno MarsOriginal Source:

It was Afrika Bambaataa and his hit Planet Rock that introduced the vocoder to the world of hip-hop in the early '80s. In the late 1990s, the Brit rockers of Radiohead played a computer-generated voice in Fitter Happier. And the intro to 24k Magic by Bruno Mars by Mr. Talkbox also featured a vocoder.

LIFE Photo Collection

It had long been assumed that Cher also used a vocoder in her worldwide hit Believe in 1997. It only emerged later that Auto-Tune, the very recently developed and commercially released audio processor, produced the distorted voice effect.

From its military applications to its use in science-fiction films through to pop, rock, and hip-hop, Homer Dudley could never have imagined what his invention would eventually be used for.

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