What stringed keyboard instrument did Leonardo da Vinci design in the 15th century?

Leonardo da Vinci designed the viola organista, a stringed keyboard instrument, in the 15th century.

The concept combined a keyboard with rotating wheels or bows that rubbed against strings, producing sound in a way related to bowed instruments. Pressing keys would select strings while a continuous mechanism supplied the friction normally created by a player’s bow. Leonardo made several drawings of related designs, but no confirmed original instrument survives.

The viola organista is often mistaken for an ordinary organ because of its name and keyboard. It produces sound from strings rather than pipes. Modern builders have created working reconstructions, showing that the principle is practical, although historians cannot know exactly which version Leonardo intended to complete.