What Leonardo da Vinci instrument used a rotating bow to make continuous music?

Leonardo da Vinci’s viola organista used a rotating bow to make continuous music.

The viola organista was a keyboard instrument Leonardo designed in the late 15th century. Pressing a key moved a string against a rotating wheel or bow, producing sound in a way that combined features of bowed string instruments and keyboard instruments. Leonardo sketched several versions, showing his attempts to solve problems involving friction, control and continuous tone.

Unlike a piano, the instrument did not strike strings with hammers. Unlike a normal viola, it allowed a keyboard player to select pitches. The design was never documented as a finished Renaissance instrument, but modern makers have constructed playable versions from Leonardo’s drawings.

The name can cause confusion because it is sometimes described as an organ. It does not use pipes in the ordinary organ sense. Its significance is that Leonardo sought to reproduce the sustained sound of bowed strings while preserving the coordinated control of a keyboard.