Leonardo da Vinci designed the viola organista, a keyboard instrument whose strings are sounded by a continuously moving bow.
Leonardo sketched the instrument in the Codex Atlanticus and other notebooks during the late fifteenth and early sixteenth centuries. Pressing keys selected strings, while a rotating wheel or belt carrying bowing material produced friction against them. The concept combined features of a keyboard instrument with the sustained sound of bowed strings.
The viola organista was never built by Leonardo, and surviving drawings show variations rather than one finalized production model. Modern makers have constructed playable interpretations. It is commonly confused with a hurdy-gurdy, but the viola organista is controlled by a keyboard, while a hurdy-gurdy normally uses keys alongside a hand-cranked wheel.