A talk box is a musical effects device that you most likely recall from the 1976 Peter Frampton song "Do You Feel Like We Do?" although its been used in a lot of music since it was developed in the 1930s. It makes the singer sound like he/she is singing through an electronic instrument. But that's not the way it works at all, and it's more difficult than you knew.
In this video, musician Lorenz Rhode sings through a talk box in a song he wrote about using a talk box. You get the idea that a lot of this is him improvising and free-associating, but it's a genuinely catchy tune. He explains that the sound is not coming from your voice at all, but from the musical instrument that's attached to the talk box, in this case a keyboard. The singer is mouthing the words, shaping the instrument's sound into words, but not using his vocal cords at all. It's hard to do, but it also allows you to breathe while holding a note. -via Laughing Squid