What Renaissance instrument did Leonardo da Vinci design using a keyboard and bowed strings?

Leonardo da Vinci designed the Renaissance keyboard-and-bowed-string instrument called the viola organista.

The viola organista combined a keyboard with strings that were sounded by continuously rotating friction wheels. Pressing keys selected the desired pitches while the wheels rubbed against the strings, creating a sustained bowed sound. Leonardo explored the idea in several manuscripts during the late fifteenth and early sixteenth centuries.

The instrument belongs to the same family of experimental designs as Leonardo’s studies of mechanical music. It was not simply a piano: piano strings are struck by hammers, whereas the viola organista used friction to imitate the action of a bow. It also was not a conventional organ, because its sound came from strings rather than pipes.

No surviving original instrument built by Leonardo is known. Modern makers have constructed playable reconstructions based on his drawings, allowing researchers and musicians to test the unusual mechanism and compare its tone with violas and other bowed instruments.