What musical instrument did Leonardo da Vinci redesign with a keyboard and multiple strings?

Leonardo da Vinci designed the viola organista, a keyboard instrument that used rotating wheels to sound strings.

The concept combined features of a keyboard and bowed string instruments. Pressing a key would bring a rotating, rosined wheel into contact with a string, producing a continuous tone in a manner related to a violin bow.

Leonardo drew several versions of the instrument, including designs with multiple strings and wheels. The idea appears in his notebooks and reflects his interest in translating musical performance into mechanical systems.

The viola organista was not a standard Renaissance instrument built and popularized by Leonardo himself. Modern makers have constructed working versions from his drawings, but the surviving sketches leave room for interpretation about exact dimensions and mechanisms.