From Zappa Wiki Jawaka
Carlotta "Mercy" Mercedes Agnes McCambridge (March, 16, 1916, Joliet, Illinois - March 2, 2004, La Jolla, California) is mentioned in "The Real Frank Zappa Book" (1989), simply as Mercedes McCambridge. Film, stage, and television actress who often played strong-willed women. Initially worked in radio dramas. Worked with Orson Welles' Mercury Theater company. Won Best Supporting Actress (Oscar) for her film debut in "All the King's Men" (1949). Played a number of support roles in such films as "Johnny Guitar" (1954), "Giant" (1956). Starred in "Run Home Slow" (1965, produced and directed by Tim Sullivan, score by FZ) and provided the, uncredited, voice-over for the demon child in "The Exorcist" (1973).