Leonardo da Vinci designed the viola organista as a stringed keyboard instrument operated by friction-driven wheels.
Leonardo’s surviving notebooks show several versions of the concept. Pressing a key would move a string against a rotating wheel, producing a sustained tone in a way that combined features of a keyboard and a bowed string instrument. The design was never completed by Leonardo as a working historical instrument.
The viola organista is often confused with an ordinary organ because of its name, but it does not produce sound through pipes. It is also different from a hurdy-gurdy, whose wheel is turned directly by a crank while the player fingers the strings.
Modern builders have reconstructed versions from Leonardo’s drawings. These reconstructions help demonstrate how Renaissance engineering connected musical performance, mechanics, and experimentation.