What keyboard instrument did Leonardo da Vinci design with strings set in motion by a wheel?

Leonardo da Vinci designed the viola organista, a keyboard instrument whose strings were set in motion by a wheel.

Leonardo’s drawings show a keyboard linked to rotating wheels or a continuous belt. Pressing a key would bring a string into contact with the moving surface, producing a sustained sound in a way related to bowed string instruments. The concept combined the expressive possibilities of a viola with the control of a keyboard.

The instrument was not a standard Renaissance keyboard instrument, and Leonardo did not leave a confirmed completed example. Several modern builders have made playable reconstructions from his surviving designs, but these reconstructions involve interpretation because the drawings do not specify every construction detail.

The viola organista is often confused with the hurdy-gurdy, which also uses a wheel to sound strings. Its distinctive feature is the keyboard mechanism that selects the notes, while the wheel provides the continuous friction needed for sound.