Leonardo da Vinci designed the viola organista using rotating bowed wheels instead of a normal bow.
The viola organista was a keyboard instrument combining ideas from the piano, string instruments, and the hurdy-gurdy. Pressing keys selected strings, while rotating wheels covered with friction material rubbed those strings continuously. This allowed the performer to produce sustained, bowed tones through a keyboard.
Leonardo sketched several versions of the instrument during the late fifteenth and early sixteenth centuries. None is known to have been completed by him, and no original Renaissance viola organista survives. Modern builders have constructed playable interpretations from his drawings.
The instrument is sometimes confused with a conventional organ because of its name. It had no pipes producing sound from air; its sound came from strings activated by rotating wheels. The design shows Leonardo’s interest in combining familiar technologies into new musical mechanisms.