Leonardo da Vinci designed the viola organista, a keyboard instrument with bowed strings.
The concept appears in Leonardo's notebooks, including the Codex Atlanticus. A keyboard controlled the notes, while rotating wheels rubbed against strings to produce a sustained sound. The design combined features associated with string instruments and keyboard instruments, allowing a performer to control pitch with keys while a mechanical system supplied the bowing action.
Leonardo explored several versions of the idea rather than leaving one universally fixed blueprint. The machine was never known to have been completed or played by him, and its exact construction has been interpreted from surviving drawings.
The viola organista is sometimes mistaken for an organ because of its name, but it does not produce sound through organ pipes. It is also distinct from a standard viol or violin, which a player bows directly. Modern builders have created working reconstructions based on Leonardo's plans.