What musical instrument did Leonardo da Vinci design using keyboards and bowed strings?

Leonardo da Vinci designed the viola organista, a keyboard instrument that produces sound with bowed strings.

The viola organista combines features of a keyboard and a string instrument. Pressing keys selects notes, while a rotating mechanism moves wheels or a continuous bowing surface against strings. This allowed one player to control pitch from a keyboard while obtaining a sustained, bowed-string tone.

Leonardo drew several versions of the idea, especially in notebooks from the late 15th and early 16th centuries. Unlike a conventional piano, the instrument was not based on hammers striking strings. Unlike an ordinary viola, it did not require the player to place a bow directly across the strings.

The design was never widely adopted in Leonardo’s lifetime. Modern builders have made experimental reconstructions, making the viola organista a notable example of Leonardo’s work joining music, mechanics, and design.