Leonardo da Vinci designed the viola organista, a keyboard instrument intended to produce continuous bowed-string sounds.
The machine appears in Leonardo's Codex Atlanticus and other surviving studies. Pressing keys would select notes while a mechanism moved a wheel or belt against strings, allowing the strings to vibrate much like those of a viola. The design combined principles from keyboard instruments and bowed instruments.
Leonardo did not leave a known completed working instrument. Later builders reconstructed versions from his drawings, showing how the concept might have operated, although details vary because the surviving plans are incomplete.
The viola organista is not an organ and does not use pipes to create its characteristic sound. Its name reflects the combination of viola-like strings with organ-style keyboard control.