What musical instrument did Leonardo da Vinci design using rotating wheels to sustain sound?

Leonardo da Vinci designed the viola organista, a keyboard instrument that used rotating wheels to sustain bowed-string sounds.

The instrument combines features of a keyboard and a stringed instrument. Pressing a key moves a mechanism so that a rotating wheel rubs against a string, producing a sound similar to that of a bowed viola. Leonardo drew several versions of the idea in his notebooks during the late fifteenth century.

Unlike a conventional organ, the viola organista does not produce its sound through pipes. It also differs from a piano because its strings are activated by friction rather than struck by hammers. The design was never built during Leonardo’s lifetime, and no original instrument survives.

Modern builders have constructed working interpretations from the drawings. These reconstructions show the concept was technically plausible, but they should not be confused with an instrument that Leonardo completed and performed.