The Vocoder (Voice Operated reCorDER) and Voder (Voice Operation DEmonstratoR)) developed by the research physicist Homer Dudley, was invented as a result of research into compression techniques for telephone voice encryption at Bell Laboratories, New Jersey USA and was the first successful attempt at analysing and resynthesising the humans voice.
The Voder was first unveiled in 1939 at the New York World Fair (where it was demonstrated at hourly intervals) and later in 1940 in San Francisco. There were twenty trained operators known as the ‘girls’ who handled the machine much like a musical instrument such as a piano or an organ, but they managed to successfully produce human speech during the demonstrations. In the New York Fair demonstration, which was repeated frequently, the announcer gave a simple running discussion of the circuit to which the girl operator replied through the Voder. This was done by manipulating fourteen keys with the fingers, a bar with the left wrist and a foot pedal with the right foot.
“At the 1939 World’s Fair a machine called a Voder was shown . A girl stroked its keys and it emitted recognsable speech. No human vocal cords entered into the procedure at any point; the keys simply combined some electronically produced vibrations and passed these on to a loud-speaker.”
(“As We May Think” by Vannevar Bush, 1945. )