Director Sir Alfred Hitchcock was so pleased with the score written by Bernard Herrmann that he doubled the composer's salary to $34,501. Hitchcock later said, "Thirty-three percent of the effect of Psycho was due to the music." Ironically, he was originally adamant that there should be no music in the shower scene but he was persuaded by his wife to give it a try. The screeching violins and dire strings (which would inspire the music for Les Dents de la mer (1975)) ending up selling the scene and driving theatrical audiences beyond anything they had ever experienced.
When the cast and crew began work on the first day, they had to raise their right hands and swear an oath not to divulge one word of the story. Alfred Hitchcock also withheld the ending part of the script from his cast until he needed to shoot it.
Director Sir Alfred Hitchcock bought the rights to the novel anonymously from Robert Bloch for only $9,000. He then bought up as many copies of the novel as he could in order to keep the ending a secret.
After this movie's release, Sir Alfred Hitchcock received an angry letter from the father of a girl who refused to have a bath after seeing Les diaboliques (1955), and now refused to shower after seeing this movie. Hitchcock sent a note back simply saying, "Send her to the dry cleaners."
Walt Disney refused to allow Sir Alfred Hitchcock to film at Disneyland in the early 1960s because Hitchcock had made "that disgusting movie, 'Psycho'".
Alfred Hitchcock: [Internalised guilt] Marion's fears of being caught by her boss and the police officer, and Norman's clean-up of the murder scene.