Leonardo da Vinci’s keyboard instrument with strings bowed by rotating wheels is the viola organista.
Leonardo developed the concept in sketches made during the late fifteenth century. The player would press keys like those on a keyboard, while a mechanism moved rotating wheels against strings. This arrangement aimed to combine the expressive sustained sound of bowed string instruments with the layout and control of a keyboard.
The viola organista was never completed by Leonardo in a known surviving instrument. Several modern builders have reconstructed versions from his drawings, and these replicas demonstrate how the mechanism could work. The idea is therefore best understood as an inventive design rather than a mass-produced Renaissance instrument.
It is sometimes confused with the hurdy-gurdy, which also uses a rotating wheel to sound strings. The key difference is that Leonardo’s design was operated through a keyboard, whereas the hurdy-gurdy normally uses a hand-cranked wheel and keys or tangents.