Leonardo da Vinci designed the viola organista, a keyboard instrument using strings and rotating bows.
The concept combined features of a keyboard with the sound-producing principle of bowed string instruments. Pressing keys would select or stop strings, while a rotating wheel or series of wheels rubbed against them to create sustained tones. Leonardo explored versions of the idea in notebooks, including designs from the late 15th and early 16th centuries.
The viola organista was never completed by Leonardo as a standard working instrument. It is sometimes confused with a hurdy-gurdy, but the mechanisms differ: a hurdy-gurdy uses a crank-turned wheel and stopped strings, whereas Leonardo’s design was keyboard-operated and sought to imitate bowed instruments. Modern builders have made playable reconstructions based on his drawings, demonstrating the ingenuity of the concept.