Rosemary Woodhouse: You're lying. It didn't die. You took it. You're lying. You witches! You're lying! You're lying! You're lying! You're lying.
Edward "Hutch" Hutchins: I see you had another suicide up there at, uh, Happy House.
Roman Castevet: To 1966! The year One.
Chosen answer: It doesn't have a specific title. It was a lullaby written for the film by Krzysztof Komeda. There's a few variations of the lullaby heard throughout the film, the opening credits version is listed as "Rosemary's Baby Main Theme - Vocal."
Bishop73