What instrument did Leonardo da Vinci design to produce continuous music with bowed strings?

Leonardo da Vinci designed the viola organista, an instrument intended to produce continuous music with bowed strings.

The concept combined features of a keyboard instrument and a stringed instrument. Pressing keys would select notes, while rotating wheels or a wheel-like mechanism would rub against strings, creating sustained sound. Leonardo made several sketches of related mechanisms, but no surviving instrument can be securely identified as his completed original.

Unlike a piano, in which hammers strike strings, the viola organista relied on friction from moving surfaces. That made it conceptually closer to bowed instruments such as the viol, even though it was played from a keyboard. The design shows Leonardo’s interest in converting mechanical motion into musical sound.

Modern builders have constructed working versions from his drawings. These reconstructions demonstrate the basic principle, but their exact sound and engineering need not match what Leonardo imagined. The name “viola organista” is a modern conventional label for the family of designs.