Harold Budd was an American composer working primarily in ambient music.
His two collaborations with Brian Eno, 1980’s The Plateaux of Mirror and 1984’s The Pearl, established his trademark atmospheric piano style.
Update: it took a Facebook comment of David Toop to bring Budd’s best work to my attention:”Bismillahi ‘Rrahman’ Rrahim” (1975):
Budd’s track on the Marion Brown Vista album:
and Budd’s own recording of that track on The Pavillion of Dreams.