What musical instrument did Leonardo da Vinci design using bowed wheels to produce sound?

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

The design combines features of a keyboard and bowed string instruments. Pressing a key lowered a string onto a rotating wheel, allowing the wheel to produce a sustained tone much like a bow. Leonardo explored the idea in several notebooks during the late 15th and early 16th centuries.

Unlike a conventional piano, the instrument was not intended to strike strings with hammers. Unlike an organ, it did not rely on pipes for its sound. Its unusual mechanism sought to give a keyboard player the expressive continuity of bowed instruments.

No known instrument built by Leonardo survives. Several modern makers have constructed working versions from his drawings, showing that the concept is mechanically feasible. The name is sometimes written “viola organista,” reflecting its hybrid character rather than a standard Renaissance instrument category.