Leonardo da Vinci designed the viola organista, a keyboard instrument using rotating wheels to imitate bowed strings.
The instrument appears in Leonardo’s notebooks, especially the Codex Atlanticus. Its keyboard controlled strings while rotating wheels rubbed against them, producing sound in a way related to a violin bow. The concept combined features of a keyboard instrument and a bowed string instrument.
Leonardo did not complete a known working viola organista during his lifetime. The design therefore belongs to the history of instrument invention rather than to a standard Renaissance instrument family. It is also unrelated to the ordinary viola, which is played with a bow held by the musician.
Several modern builders have constructed versions from Leonardo’s drawings. These reconstructions help performers and historians investigate how the proposed wheel-and-string mechanism may have sounded.