What musical instrument did Leonardo da Vinci invent using rotating wheels to bow strings?

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

The design combines features of a keyboard and a bowed string instrument. Pressing keys selects strings, while one or more continuously rotating wheels create friction against them, producing a sustained tone. Leonardo drew several versions during the late fifteenth and early sixteenth centuries.

The viola organista was never completed by Leonardo as a known working instrument. Its name is modern and reflects the instrument’s hybrid character: it sought to produce the expressive sound of bowed strings through a keyboard mechanism. This differs from a harpsichord, whose strings are plucked, and a clavichord, whose strings are struck.

The concept fascinated later instrument makers. Modern reconstructions have demonstrated that the mechanism can produce sound, although they are interpretations of Leonardo’s drawings rather than surviving original instruments. The invention shows his interest in linking mechanical motion with musical expression.