Leonardo da Vinci invented the viola organista, a keyboard instrument using rotating wheels to create continuous sound.
Leonardo developed designs for the instrument during the late fifteenth and early sixteenth centuries. Pressing keys would bring strings into contact with rotating wheels, allowing the wheels to bow the strings and produce sustained tones.
The idea combined features of a keyboard, a bowed string instrument, and a wheel-driven mechanism. It was not simply a normal organ: the sound came from strings, while the performer controlled pitch through keys.
No complete Leonardo-built viola organista survives, and the instrument was not widely adopted in his lifetime. Modern builders have made reconstructions based on his drawings. The name is sometimes confused with the hurdy-gurdy, but the viola organista uses a keyboard rather than a hand-turned crank.