Leonardo da Vinci’s viola organista was a keyboard instrument designed to produce sound from continuously bowed strings.
Leonardo drew several versions of the instrument, probably during the late fifteenth century. Pressing a key would move a string against a rotating wheel or belt, allowing the player to control pitch from a keyboard while the mechanism supplied sustained friction. The concept combined features associated with the viola family and the organ or keyboard tradition.
The viola organista was never completed by Leonardo as a surviving working instrument. It is therefore more accurate to call it a design than a successful Renaissance invention in regular use. Contemporary builders have made reconstructions based on his drawings, but details vary because the sketches leave room for interpretation.