What musical instrument did Leonardo da Vinci design with keyboard keys and bowing wheels?

Leonardo da Vinci designed the viola organista, a keyboard instrument with bowing wheels.

Leonardo developed several versions of the idea during the late fifteenth and early sixteenth centuries. Pressing a key would select a string, while rotating wheels covered with horsehair or another friction material would bow the strings. The concept combined the expressive, sustained sound of bowed instruments with the layout and control of a keyboard.

Unlike an ordinary organ, the viola organista did not produce sound by sending air through pipes. Unlike a piano, its strings were not struck by hammers. That hybrid mechanism made it an unusual member of the keyboard-instrument family. Leonardo’s drawings show mechanical details, but no surviving original instrument is known.

The design was not simply a fanciful musical sketch. Later instrument makers built reconstructions based on Leonardo’s plans, demonstrating that the mechanism could produce sound. The name can also cause confusion because “viola organista” is used for modern reconstructions as well as Leonardo’s historical concept.