Leonardo da Vinci invented the viola organista, a keyboard instrument designed to bow strings continuously.
Leonardo drew several versions of the instrument in his notebooks, especially the Codex Atlanticus. Its keyboard operated mechanisms that pressed strings against rotating wheels or bows. This allowed a player to control pitch and rhythm with keys while a continuous friction system produced the sound.
The viola organista combined features associated with bowed string instruments and keyboard instruments. Unlike a conventional organ, it did not use pipes, and unlike a normal viola, it did not require a handheld bow. Leonardo's surviving designs vary, so modern reconstructions do not all use exactly the same mechanism.
The instrument was not widely produced during Leonardo's lifetime. Modern builders have created working interpretations, but these reconstructions are based on incomplete drawings and require engineering choices. The name is sometimes confused with the organ, yet the central idea is mechanical bowing of strings.