Leonardo da Vinci designed the viola organista, a keyboard instrument that used moving wheels to bow strings continuously.
The instrument appears in Leonardo’s notebooks, especially studies associated with the late 15th century. Pressing keys would select strings, while rotating wheels covered with horsehair or another suitable material would produce friction and sustain the sound, combining features of a keyboard and bowed instrument.
The viola organista was not a standard Renaissance instrument and did not become a commercial musical tradition. Its surviving drawings are design studies rather than evidence that Leonardo completed a fully working original instrument.
It is sometimes confused with an organ because of its keyboard, but it does not make sound through organ pipes. Modern builders have reconstructed versions from Leonardo’s plans, showing how the mechanism might have worked.