What keyboard instrument did Leonardo da Vinci design to produce bowed-string sounds?

Leonardo da Vinci designed the viola organista as a keyboard instrument intended to produce bowed-string sounds.

The design uses a keyboard to control strings while rotating wheels or bowing mechanisms create continuous friction, somewhat combining features of a piano and a bowed string instrument. Pressing keys would select the notes, while the mechanical system would make the strings vibrate.

Leonardo drew several versions of the concept during the Renaissance, but he did not complete a known working instrument. The design is therefore an invention preserved mainly through drawings rather than a device that became a standard musical instrument.

The viola organista is sometimes confused with the hurdy-gurdy because both use friction to sound strings. The key distinction is that Leonardo’s design is played with a keyboard, whereas a traditional hurdy-gurdy is operated with a hand-cranked wheel and keys.