Which string instrument did Leonardo da Vinci design to play continuously with a wheel?

Leonardo da Vinci designed the viola organista, a keyboard instrument whose strings were sounded by a rotating wheel.

Leonardo sketched several versions of the instrument in notebooks during the late 15th and early 16th centuries. Pressing keys moved strings against a wheel covered with material similar to a bow, producing sustained tones. The concept combined the keyboard layout of an organ or harpsichord with the continuous sound of bowed strings.

Unlike a standard harpsichord, the viola organista was not based on plucking strings. Unlike a conventional viola, it did not require a bow held directly by the player. The design also differed from a hurdy-gurdy because the keyboard selected pitches while the wheel supplied the friction.

No authenticated Leonardo-built viola organista survives. Polish musician Sławomir Zubrzycki completed a playable reconstruction in 2013, based on Leonardo’s drawings and related historical sources. The instrument demonstrates that the design was mechanically plausible, even though it never became a mainstream Renaissance instrument.