Leonardo da Vinci designed the viola organista as a keyboard instrument with continuously bowed strings.
The concept appears in Leonardo’s notebooks, especially the Codex Atlanticus and the Madrid manuscripts. Pressing a key would select a string, while a rotating wheel or belt covered with horsehair would rub against the strings and produce a sustained sound. The design combined the keyboard layout of an organ or harpsichord with the bowed tone of a string instrument.
Leonardo did not leave a confirmed surviving full-size instrument, and the viola organista was not established in Renaissance musical practice. Its name is modern and descriptive rather than evidence that Leonardo built a standard viola.
Several modern makers have reconstructed versions from the drawings. These instruments demonstrate the principle, but details vary because Leonardo’s sketches do not provide one complete, unambiguous construction plan. The viola organista is therefore best understood as an inventive musical concept, not a widely used historical instrument.