Leonardo da Vinci designed the viola organista, a keyboard instrument with bowed strings, in the late 15th century.
The instrument combined a piano-like keyboard with a mechanism that moved a wheel, or a series of wheels, against strings. Pressing a key selected a string while the rotating wheel supplied continuous friction, producing a sound related to bowed string instruments.
Leonardo drew several versions in his notebooks, but there is no evidence that he completed a playable original instrument. Modern builders have reconstructed versions from his designs, showing how the concept could work in practice.
The viola organista is often confused with an ordinary organ because of its keyboard, but it does not produce sound through organ pipes. It is also not the same as the later hurdy-gurdy, which uses a hand-turned wheel and stopped strings rather than a keyboard mechanism.