Although primarily a stage actor, he is best-known for voicing HAL 9000, the supercomputer in the film 2001: A Space Odyssey (1968) and its sequel 2010: The Year We Make Contact (1984).

[5] He performed a wide variety of theatrical roles, such as a production of Henry V staged in Stratford, Ontario, that was adapted for television in 1966.

[9] In the film, his voice was also sometimes processed with an electronic device called the Eltro information rate changer.

He also briefly parodied it in a sketch on Second City Television where Merv Griffin (played by Rick Moranis) takes his talk show into outer space.

[10] Rain was married twice, first to Lois Shaw and then to Martha Henry, who was also an actress on stage, film and television, and had three children and a grandchild.