Leonardo da Vinci designed the viola organista, a keyboard instrument that produced sound from bowed strings.
The player would press keys, while a mechanism brought rotating wheels or a continuous bowing surface into contact with the strings. This combined the expressive sustain associated with bowed instruments with the layout and control of a keyboard.
Leonardo drew several related concepts in his notebooks, but he did not leave a surviving, fully documented instrument that can be identified as a completed original. Modern builders have created reconstructions based on his sketches, with different interpretations of the mechanism.
The viola organista should not be confused with a normal organ or harpsichord. Those instruments produce sound through pipes or plucked strings, whereas Leonardo's concept depended on friction between a moving bowing element and strings.