Leonardo da Vinci designed the viola organista, a bowed keyboard instrument using rotating bows.
The instrument combined a keyboard with strings and a continuous bowing mechanism. When a key was pressed, the corresponding string could contact a rotating wheel or belt covered with horsehair, producing a sustained bowed sound. Leonardo drew several versions of the idea in his notebooks during the late 15th and early 16th centuries.
The viola organista was intended to make the expressive sound of bowed strings playable from a keyboard. Unlike a harpsichord, which plucks strings, it sought to imitate instruments such as the viola through friction and continuous bow movement.
Leonardo’s original instrument is not known to have survived or been completed. Modern builders have created reconstructions based on his drawings, and the design is sometimes confused with the hurdy-gurdy, which uses a hand-cranked wheel but has no keyboard-driven bowing system of this type.