That would be a HFO, or high-frequency ocillator.
It's just one note, and you could change the pitch in a number of ways. But, are you thinking about notes from the strings and frets? That would involve putting wires to every fret (inside the neck) and having each string issolated so that when they make contact, they tell the HFO what note to produce.
Oh yeah, they made this already back in the 70's. The Guitorgan, I think, and legend has it that Edgar Winter used one to play Frankenstein!
da-da-da-dah, da-da-dah-daaaaaaah, da-da-dah-do-dah.