Leonardo da Vinci’s viola organista combined a keyboard with continuously moving bowed strings.
The instrument was designed to produce sound when strings were pressed against a rotating wheel or belt covered with bowing material. A keyboard controlled which strings were stopped, while the moving bow created sustained tones. In principle, it joined the expressive sound production of a bowed string instrument with the player control of a keyboard.
Leonardo drew several versions of the idea in his notebooks during the Renaissance. The instrument was never known to become a standard working part of European musical life, and no surviving original instrument by Leonardo has been established. Modern builders have made reconstructions based on his drawings.
The viola organista is sometimes described as a piano, but it is not a piano: a piano strikes strings with hammers. It is also different from an ordinary organ, which produces sound through pipes. Its distinctive feature is the combination of keyboard selection and mechanical bowing.