SAN FRANCISCO — In December 1968, the computer scientist Douglas Engelbart sat on a stage here and introduced the world to modern computing. He brought together for the first time a mouse, word processing, multimedia communication and networking to demonstrate interactive computing before an audience of a thousand leading computer scientists. His presentation would become known as the Demo.

It was the moment at which computing went from being viewed merely as a tool for calculating to being seen as a digital medium for expression in its own right. On April 1, the composers Ben Neill and Mikel Rouse will perform their new musical theater work based on the Demo at the Bing Concert Hall at Stanford University.

Mr. Rouse will play Dr. Engelbart, who on that day appeared at this city’s Brooks Hall in front of a keyboard that was flanked by a mouse and another control device known as a key-chord set. He wore a headset, and at his back was a 20-foot-high video screen displaying the output on his desktop monitor. The system was connected via a wireless link to programmers and hardware engineers 30 miles south in Menlo Park, who watched the demonstration in real time thanks to a video camera run by the Whole Earth Catalog publisher Stewart Brand.

The presentation electrified the computing world, which was then still based on hidden mainframe computers laboriously programmed with decks of key punch cards. Chuck Thacker, a young computer engineer at the time who witnessed the event, would later say that Dr. Engelbart sat onstage “dealing lightning with both hands.”