What musical instrument did Leonardo da Vinci design using strings activated by a keyboard?

Leonardo da Vinci designed the viola organista, a keyboard instrument whose strings are activated by rotating friction wheels.

Leonardo developed several versions of the idea in notebooks, especially during the late fifteenth and early sixteenth centuries. Pressing keys was meant to bring individual strings into contact with rotating wheels, producing sustained bowed-string sounds while allowing keyboard-style playing.

The instrument combined features associated with a keyboard and a string ensemble. It was not simply a conventional organ: air and pipes were not the source of its sound. Nor was Leonardo’s drawing a completed surviving instrument.

Modern builders have reconstructed versions from his plans, although the exact historical design is debated because Leonardo left several variants rather than one final specification. The name “viola organista” was applied to the later reconstructed concept.