Leonardo da Vinci designed the viola organista, a musical machine that used bowed wheels to imitate the sound of a string ensemble.
The instrument combined features of a keyboard and bowed string instruments. Pressing keys selected strings, while rotating wheels rubbed against them and produced sound. This arrangement allowed one performer to control several notes from a keyboard, much as an organist controls pipes or a pianist controls strings through keys.
Leonardo sketched the idea in the late 15th century, but he did not leave a confirmed surviving working instrument. The machine is often described as a mechanical experiment rather than a finished commercial instrument. Its name reflects its hybrid nature: it was intended to produce sustained, bowed tones through a keyboard mechanism.
Modern builders have reconstructed versions from Leonardo’s drawings. The viola organista is sometimes mistakenly called a conventional organ, but it uses strings and friction wheels rather than air-filled pipes. That mechanical distinction is the key to understanding the invention.