What Leonardo da Vinci invention played music with bowed strings operated by a keyboard?

Leonardo da Vinci's viola organista was a keyboard instrument with bowed strings.

Leonardo sketched the concept in several notebooks during the late 15th and early 16th centuries. Pressing keys was intended to bring strings into contact with rotating wheels or a continuous bowing surface, allowing the player to produce sustained tones. The design combined the control of a keyboard with the sound-producing principle of a string instrument.

Unlike a normal viola, the instrument did not require a separate bow moved by the player's hand. Unlike a pipe organ, it produced sound from vibrating strings rather than air in pipes. Leonardo's drawings show more than one possible arrangement, so reconstructions are not identical.

No securely documented Leonardo-built original survives. Modern makers have built working versions based on his sketches, demonstrating the mechanical idea while necessarily making interpretive choices about missing details.