What was Leonardo da Vinci’s viola organista designed to use against strings?

Leonardo da Vinci’s viola organista was designed to use rotating wheels against strings.

The instrument’s central idea was to make strings vibrate through friction. A player would press keys, and the mechanism would bring strings into contact with rotating wheels or wheel-like surfaces. This arrangement was intended to create sustained tones while preserving the control of a keyboard.

The concept drew on the sound-producing behavior of bowed instruments. A violin uses a bow moving across a string, whereas a harpsichord plucks its strings and a piano strikes them with hammers. Leonardo’s design tried to translate the continuous action of a bow into a mechanically driven keyboard instrument.

Leonardo produced multiple sketches, but the viola organista did not become a standard instrument in his lifetime. Modern reconstructions have clarified how the mechanism could work, although builders make design choices where the notebooks are incomplete. The rotating wheels, rather than hammers or plectrums, are the defining feature of the concept.