Leonardo da Vinci’s keyboard instrument with strings played by a rotating wheel was the viola organista.
The viola organista combines ideas from a keyboard instrument and a bowed string instrument. Pressing keys moves strings against a rotating wheel, producing sound in a manner related to a violin bow. Leonardo drew several versions of the mechanism during the late 15th and early 16th centuries.
The instrument was intended to let one performer control pitch with a keyboard while the wheel supplied continuous friction against the strings. This differed from ordinary keyboard instruments such as the harpsichord, whose strings are plucked, and the clavichord, whose strings are struck or touched by tangents.
Leonardo did not leave a complete surviving instrument, but modern builders have reconstructed versions from his drawings. The name “viola organista” is used for the family of instruments based on this wheel-and-string principle, including reconstructions made centuries after Leonardo’s sketches.