Talkbox
A speaker driver that pipes an instrument's sound through a tube into the player's mouth, where it gets shaped into words.
Signal from a guitar or synth goes to a driver that pushes the sound into a plastic tube. The player holds the tube in their mouth and mouths vowels and consonants without using their vocal cords; the mouth cavity acts as a filter and imposes speech formants. A microphone in front of the face picks up the result. It's pure acoustics, which is why it sounds more physical than a vocoder, which does the equivalent job with filter banks.
Precursors existed as early as 1939, but Bob Heil's talkbox from 1973 and Peter Frampton's live album a few years later made it famous. Roger Troutman of Zapp turned it into a funk signature. The drawbacks are well documented: loud sound straight into the mouth, a lot of saliva, and an audience wondering why the guitarist is chewing on a hose.