What Leonardo da Vinci invention combined a bowed instrument with keys like a keyboard?

Leonardo da Vinci's viola organista combined a bowed instrument with keys like a keyboard.

Leonardo developed designs for the viola organista in the late 15th and early 16th centuries. The instrument used a keyboard to control strings, while rotating wheels or belts rubbed against them like a continuously moving bow. This arrangement allowed a performer to select notes with keys while producing a sustained bowed sound.

The idea sits between a string instrument and a keyboard instrument. It was not an organ in the usual pipe-based sense, despite its name, and it was not simply a piano. Leonardo made several drawings, suggesting that he continued refining the mechanism rather than recording one finished standard model.

The instrument was not known to have been built by Leonardo. Modern makers have constructed playable versions from his sketches, showing how the keyboard could operate the bowing system. Its importance lies in combining controllable pitch selection with the expressive sound associated with bowed strings.