Leonardo da Vinci invented the viola organista by combining features of a bowed string instrument and a keyboard.
The viola organista used a keyboard to control rotating wheels or bows that sounded strings. Pressing keys selected pitches, while the mechanism brought the strings into contact with continuously moving friction surfaces. This allowed one player to produce sustained tones without holding a conventional bow.
Leonardo drew several versions of the instrument in his notebooks, especially in the Codex Atlanticus. His sketches show changing arrangements of strings, wheels, and controls, so historians do not treat every drawing as one final standardized model.
The viola organista was never a mainstream Renaissance instrument. Modern builders have reconstructed versions from Leonardo’s designs, demonstrating the unusual link between keyboard technique and bowed-string sound. It should not be confused with the ordinary viola, which is played with a hand-held bow.