Leonardo da Vinci designed the viola organista to combine bowed strings with a keyboard.
The instrument used a keyboard to control friction between strings and rotating wheels or bows. Pressing a key would bring a string into contact with the moving mechanism, producing a sustained tone in a way that resembled a viola or other bowed string instrument.
Leonardo drew several versions of the idea during the fifteenth and early sixteenth centuries. Unlike a harpsichord, which plucks strings, or a piano, which strikes them, the viola organista was intended to produce sound through continuous friction.
No evidence shows that Leonardo completed a playable original instrument. Modern builders have constructed working versions from his drawings, but these reconstructions necessarily interpret incomplete plans. The design is therefore best understood as an inventive keyboard-string experiment rather than the direct ancestor of one standard modern instrument.