Leonardo da Vinci designed the viola organista, a keyboard instrument whose strings were sounded by rotating friction wheels.
Leonardo drew several versions of the idea in his notebooks during the late 15th and early 16th centuries. Pressing keys would select strings, while a rotating wheel or wheels would rub against them, producing sound in a way related to bowed string instruments. The keyboard allowed one player to control multiple strings more easily than on a conventional viola.
The viola organista was never completed by Leonardo as a documented working instrument. Modern builders have constructed versions from his drawings, but these reconstructions are interpretations because the surviving sketches do not provide every manufacturing detail.
The name can cause confusion: “organista” refers to the keyboard mechanism, not to pipe-organ construction. The concept belongs to Leonardo’s broader studies of music, mechanics, and automated motion.