Leonardo da Vinci designed the viola organista, a keyboard instrument using bowed strings and a continuously moving bow.
Leonardo’s surviving sketches show several related mechanisms. Pressing keys would bring strings into contact with rotating wheels or a moving bowing surface, producing sustained tones in a way that combined features of a keyboard instrument and a bowed string instrument. The concept was intended to make bowed-string sounds playable from a keyboard.
Unlike a normal viola, the viola organista did not require a player to hold a bow in one hand. Unlike an organ, it produced sound from strings rather than pipes. Leonardo did not leave a documented completed instrument, so the surviving evidence consists mainly of drawings and mechanical proposals.
Modern makers have constructed working interpretations, including instruments based on the Codex Atlanticus designs. These reconstructions demonstrate that the idea can produce music, but they should not be confused with an original Leonardo instrument preserved from the Renaissance.