Viola organista

The viola organista is a musical instrument designed by Leonardo da Vinci. It uses a friction belt to vibrate individual strings (similar to how a violin produces sounds), with the strings selected by pressing keys on a keyboard (similar to an organ). Leonardo's design has intrigued instrument makers for more than 400 years, but though similar instruments have been built, no extant instrument constructed directly from Leonardo's incomplete designs is known. Sometimes it is mistakenly referred to as the harpsichord viola, which is a different instrument.