Leonardo da Vinci designed the viola organista, a keyboard instrument that uses a bowing mechanism to produce string sounds.
Leonardo sketched the instrument in the late 15th century. Pressing keys was intended to bring rotating, rosined wheels or a continuous bow into contact with strings, combining the controls of a keyboard with the sustained sound of bowed instruments.
The design was never built by Leonardo, and surviving drawings do not specify every construction detail. This makes modern reconstructions interpretive rather than exact copies. The instrument is sometimes confused with a hurdy-gurdy, but a hurdy-gurdy uses a hand-turned wheel and stopped strings, while Leonardo's concept was operated from a keyboard.
Several modern makers have built working versions based on Leonardo's drawings. The viola organista therefore belongs to the history of experimental musical instruments rather than to the standard orchestra.