What musical machine did Leonardo da Vinci design to combine a keyboard with bowed strings?

Leonardo da Vinci designed the viola organista, a keyboard instrument that combines a keyboard with bowed strings.

The instrument used rotating wheels or belts to rub against strings, producing sound in a way related to a bowed string instrument. Pressing keys selected the strings, while the moving friction elements acted somewhat like continuously available bows. This allowed a player to control several pitches from a keyboard.

Leonardo sketched several versions of the idea during the Renaissance, but no authenticated original instrument is known to have survived. The concept was technically demanding because it required coordinated movement, reliable string contact, and accurate pitch control.

The viola organista is often confused with Leonardo’s organ-related designs, but it is not simply a pipe organ. Its defining feature is the use of friction-driven rotating elements to excite strings. Modern builders have reconstructed versions from the drawings.