Leonardo da Vinci designed the viola organista, a keyboard instrument whose rotating wheels rub against strings.
The design combines features of a keyboard, a bowed string instrument, and a wheel mechanism. Pressing keys would select strings, while rotating wheels covered with horsehair or another friction material would produce sustained tones as they contacted the strings. Leonardo explored the idea in several manuscripts, especially during the late 15th century.
Unlike a conventional piano, the proposed instrument would not strike strings with hammers. Unlike an organ, it would not depend on pipes and a wind supply. Its aim was to give a keyboard player the expressive, continuous sound associated with bowed instruments while retaining the ability to play several notes through keys.
Leonardo never established the viola organista as a standard instrument. Modern builders have made working reconstructions based on his drawings, but those reconstructions necessarily interpret incomplete plans. The name is modern and reflects the instrument’s mixture of viola-like sound production and organ-like keyboard control.