Leonardo da Vinci designed the viola organista, an instrument using a rotating wheel to press bows against strings.
The viola organista combined features of a keyboard and a bowed string instrument. Pressing keys selected strings, while a rotating wheel covered with horsehair or another friction surface rubbed them and produced a sustained sound. Leonardo explored several versions of the idea in notebooks from the late 15th and early 16th centuries.
The concept addressed a limitation of ordinary bowed instruments: a player could not easily sustain many notes at once. A keyboard mechanism could control several strings, potentially allowing chords and continuous tones. The instrument was never completed by Leonardo as a finished, standardised musical product.
The name is modern and descriptive, linking the sound of a viola with the playing method of an organ keyboard. Several modern builders have constructed working replicas, but those instruments interpret Leonardo’s surviving drawings rather than reproduce one fully documented original.