What machine did Leonardo da Vinci design to play music using a keyboard and rotating bows?

Leonardo da Vinci designed the viola organista to play music using a keyboard and rotating bows.

The viola organista combines features of a keyboard instrument and a bowed string instrument. Pressing keys selects strings, while a continuous belt or wheel mechanism moves a bow across them. Leonardo explored versions of the idea in drawings made during the late 15th and early 16th centuries. The device was intended to produce sustained bowed tones without requiring a separate performer to move a bow by hand.

The name refers to the instrument’s hybrid character: it has the keyboard action of an organ or keyboard instrument and the sound-producing principle of a viol. Leonardo’s surviving drawings show concepts rather than a confirmed original instrument that he completed.

Several modern builders have reconstructed or interpreted the viola organista. It should not be confused with Leonardo’s mechanical lion or his studies of church organs; those were different projects and mechanisms.