Marilyn Monroe memorably sang the song, 'That Old Black Magic' in the movie, Bus Stop (1956). She performed it in more of her breathy voice rather than her competent singing voice. Monroe probably wanted to purposefully sound unprofessional when singing the song, especially considering that the setting at the time was a skimpy night-club.

Monroe's character Cherie was singing the song to an audience who is not listening and talking loudly; Don Murray ( Beauregard "Beau" Decker) quieted them all down. Cherie's rendition of "That Old Black Magic" entrances Beau. He then forces Cherie outside of the club, despite the establishment's rules against it. They kiss and Beau thinks that means they are engaged. Chérie is physically attracted to him; but, resists his plans to take her back to Montana. She has no intention of marrying him and tells him that she cannot marry him. He is too stubborn to listen her.

Beau whose intentions are honorable, can't control his temper and can't understand why Cherie won't take him seriously. Because she rejects him, he begins acting jealous and possessive. Love in this instance takes some lumps, but it nonetheless comes out slugging. Marilyn as Cherie is vulnerable and jaded. But in the end, she is willing to take a big chance on love with Beau.

More Info: en.wikipedia.org