What Leonardo da Vinci invention combined a bow with a keyboard to produce continuous music?

Leonardo da Vinci's viola organista combined a keyboard with bowed strings to produce continuous music.

Leonardo sketched the instrument in several notebooks during the late 15th and early 16th centuries. Pressing a key was intended to move a wheel or bowing mechanism against strings, allowing the performer to control pitch from a keyboard while producing a sustained, bowed sound.

The design belongs to Leonardo's experiments with musical instruments and mechanical systems. It was not a conventional organ: an organ uses air pipes, whereas the viola organista used strings. It was also unlike a normal violin because the player did not bow each string directly with a handheld bow.

No confirmed original Leonardo viola organista survives. Modern instrument makers have built versions from his drawings, and these reconstructions show that the concept is mechanically feasible. The instrument is therefore best understood as a Renaissance design and an ancestor of later keyboard-string experiments.