What Leonardo da Vinci machine used keys to play strings with a bowing mechanism?

Leonardo da Vinci’s viola organista was a keyboard instrument that used keys to activate bowed strings.

Leonardo designed the instrument in the late 15th century and revisited the idea in several drawings. Pressing a key was intended to bring a string into contact with a rotating wheel or belt, producing a sustained sound in the manner of a bowed string instrument. The keyboard made it possible for one performer to control the pitches.

The instrument combined features associated with organs, keyboards, and violas. It was not a conventional organ because its sound came from strings rather than pipes, and it was not an ordinary viola because the performer used keys instead of a bow held directly in the hand.

No surviving Renaissance example proves that Leonardo completed a working version. Modern builders have constructed playable instruments from his drawings, showing that the underlying concept can work.