Leonardo da Vinci designed the viola organista, a keyboard instrument that produces sound from bowed strings. Its keys operate mechanisms that bring rotating wheels or bows into contact with strings, blending features of a keyboard and a bowed instrument.
Leonardo developed several versions of the idea in sketches from the late 15th and early 16th centuries. Unlike a conventional piano, in which hammers strike strings, the viola organista uses continuous friction to make the strings vibrate. This could allow sustained tones while preserving keyboard control over pitch.
No completed Leonardo viola organista is known to have survived. The instrument therefore remained an ingenious design rather than a standard Renaissance performance instrument.
The name can cause confusion because “viola organista” is also used for modern reconstructions. Contemporary builders have made playable versions based on Leonardo's drawings, but those instruments are reconstructions, not original surviving machines made by Leonardo himself.