What keyboard instrument did Leonardo da Vinci design with a bow moved by a wheel?

Leonardo da Vinci designed the viola organista, a keyboard instrument whose strings were sounded by a rotating wheel.

The player would press keys like those of an organ or keyboard while a bowing mechanism brought strings into contact with a continuously turning wheel. This allowed the instrument to produce sustained bowed-string sounds while keeping the keyboard layout familiar.

Leonardo drew several versions during the late fifteenth and early sixteenth centuries. None is known to have been built by him, and the instrument remained a design rather than a standard Renaissance concert instrument. Modern makers have constructed working replicas from the drawings.

The viola organista is often mistaken for a piano because both use keys. A piano strikes strings with hammers, while Leonardo’s design uses friction from a bowing wheel. The name refers to its combination of viola-like sound production and organ-like keyboard control.