Leonardo da Vinci designed the viola organista, a keyboard instrument that used rotating, rosined wheels to make strings sound.
The instrument combined features of a string instrument and a keyboard. Pressing keys selected strings, while turning a crank rotated the friction wheels. The wheels acted somewhat like the bow of a violin, continuously exciting the strings and producing sustained tones.
Leonardo drew several versions of the idea, but no surviving original instrument is known. Modern builders have made reconstructions from his notebooks, showing how the mechanism could produce sound. The design illustrates his interest in joining mechanical control with musical expression.
The viola organista is not simply a keyboard version of a violin. A piano strikes strings with hammers, while a harpsichord plucks them. Leonardo's instrument instead relies on friction between moving wheels and strings, giving it a distinctive place among historical keyboard experiments.