The Voder, developed by Bell Labs, is recognized as the world's first speech synthesizer (previously at Boing Boing). Played like a musical instrument, performance required such skill and experience that it took a year to train an operator. The video below, from 1939, shows Helen Harper at work.
Software engineer Griffin Moe explains what she's doing, exactly, and recreated the Voder's user interface online. Think "QWOP but for speaking," and you're off to the races.