Here's a little YouTube video that P Thugg from synth-pop powermasters, Chromeo sent me. Incredible 60s talkbox action from session musician ledgend and steel guitar whizz-kid, Pete Drake.
Here's some more info from Wikipedia:
His innovative use of what would be called the "talk box", later used by Peter Frampton, Joe Walsh and Jeff Beck, added novel effects to the pedal steel guitar. The album Pete Drake and His Talking Steel Guitar, harkened back to the sounds of Alvino Rey and his wife Luise King, who first modulated a guitar tone with the signal from a throat microphone in 1939. The unique sound of the talk box with a steel guitar was new in the 1960s, and it made the sounds of vocalizing along with the strings of the steel guitar.
"According to an interview of Pete Drake "You play the notes on the guitar and it goes through the amplifier. I have a driver system so that you disconnect the speakers and the sound goes through the driver into a plastic tube. You put the tube in the side of your mouth then form the words with your mouth as you play them. You don't actually say a word: The guitar is your vocal cords, and your mouth is the amplifier. It's amplified by a microphone."
PLUS - If you missed it, check out the video below of Chromeo playing with Daryl Hall from 80s Pop superstars, Hall & Oates - amazing stuff!