Xerox Mockingbird (1980)

Mockingbird (circa 1980) is credited as the first screen-based visual notation editor for musicians. The software was a research project of Xerox PARC and was never released commercially. It ran on the Dorado system - a successor to the Xerox Alto, and supposedly host to the famous Smalltalk demo presented to Steve Jobs and Apple engineers that sparked the Lisa and Macintosh interfaces.