In 1955, he joined MIT's Lincoln Laboratory as a programmer and designer for the SAGE air-defense system.
He moved with the team to Washington University in St. Louis where he was one of the principal designers of macromodules.
In 1972 he headed the first delegation of U.S. computer scientists to the People's Republic of China.
[2] In 1976, he joined Xerox PARC where he implemented a computer interface to an early laser printer.
[3] Ornstein co-designed Mockingbird, the first interactive computer-based music-score editor, and oversaw its programming.