What musical instrument did Leonardo da Vinci design using continuously rubbed wheels?

Leonardo da Vinci designed the viola organista, a keyboard instrument using continuously rubbed wheels.

Leonardo’s surviving drawings show a keyboard connected to strings and rotating wheels. Pressing a key would bring a string into contact with a wheel covered or treated to create friction, producing a sustained sound somewhat related to that of bowed string instruments.

The viola organista combined features of a keyboard and a string instrument. Unlike a piano, whose hammers strike strings, and a harpsichord, whose jacks pluck them, Leonardo’s concept aimed to make the wheels act like mechanical bows.

No single authoritative design was built by Leonardo himself, and later builders interpreted his sketches in different ways. Modern reconstructions have demonstrated that the principle can produce music, but they are reconstructions rather than surviving original instruments.