The Voder was operated (or “played” in the language of the Voder’s creators) almost entirely by Helen Harper, writes Eric Grundhauser for Atlas Obscura. Harper also trained others to operate it–no small feat. The machine could create "20 or so different buzzes and chirps," Grundhauser writes, "which the operator could manipulate using 10 keys, a wrist plate and a pedal.”
The result, in a 1939 recording in which Harper plays the Voder, is startling. First, Harper makes Pedro say “she saw me.” The result is intelligible but monotonous–not much like Siri, who is voiced by real people.
Then, taking the machine through its paces, she is able to transform the Voder’s words from statements to questions, where the inflection goes up at the end of the sentences. She even has it speak in different voices–both male and female, although the Voder team referred to the machine as male. Taking a page from Thomas Edison’s tinfoil recordings, the Bell team had Pedro recite “Mary Had a Little Lamb” in all of its different voices:
Later that year, the Voder finished up its publicity run at the Golden Gate International Exposition in San Francisco. Then, writes Grundhauser, “the machine disappeared almost instantly.” Bell used it to show off, but wasn’t intending to sell it, he writes—which might have been a good thing. Pedro’s voice sat firmly in the Uncanny Valley: it sounded (mostly) human, but really, really wasn’t.
Pedro was particularly significant for its time because the machine made human sound without using a humanoid method, like breathing air or having “lungs” and a “throat,"writes sonic historian Jacob Smith. That was unlike previous devices that made human-like sound, like Euphonia, Edison’s phonograph (which resembles a throat) or Jacques de Vaucanson’s eighteenth-century Flute Player.
As a 1939 LIFE magazine article explains, while people make sound waves by manipulating air, vocal cords and mouth shape, the Voder instead makes electrical vibrations that translates into sound waves in the loudspeaker.
Smith notes that the invention received major press coverage for its time—and for good reason. “The Voder was one of several voice technologies to have a significant impact on radio and film production during the 1940s,” he writes.
The Voder wasn’t sentient. There wasn’t the remotest possibility that it could learn to “play” itself and truly speak in its own voice. But still–it had a voice.