This awesomely strange 1940 film demos the incredible Sonovox – a electroacoustic precursor to the vocoder.

Kay Kyser’s band in You’ll Find Out.

And it even swings. For a moment.

via MisterScott99:

The Sonovox consists of one or two louspeakers placed on the throat that play the source sound. The performer whispers the words while the speakers stand in for the voice box.

Used for the talking train in Disney’s Dumbo, uncountable radio promos. A tube-in-the-mouth version Talk Box was used by Frampton to make his guitar sing, and all-electronic Vocoder versions are still used in current pop music.