That whispery, babyish voice was a Marilyn Monroe trademark. It is rumored that Jackie Kennedy adopted that voice after the affair began between her husband and Marilyn. Marilyn’s voice was as much her signature as her platinum blonde hair. In spite of her voice’s appeal, Marilyn’s natural voice was far superior and much sexier. It was nothing like the voice she used in later films in her career. In early films, she used her own natural voice. When she acted roles using her real voice she came across as a more competent, more real actress. As Evie, in Dangerous Years, her voice is very different from her later affect. She is a good actress in this small role probably because it doesn’t present Marilyn in a dumb blonde role.
Even her singing voice in Ladies of the Chorus is far superior to the baby-doll singing voice she developed later in her career. Contrast the Chorus solo to Sugar Cane’s in Some Like it Hot. Marilyn is a talented singer with a pretty voice regardless of which voice she uses. Her authenticity however is more apparent in her earlier songs. Her voice isn’t manufactured. It’s earthy. It’s sultry. In her later films, Marilyn’s voice becomes wispy, childish, and conjures to mind the “dumb blonde” image she sought to overcome.
Marilyn’s voice during private interviews was also strikingly different from the voice she used in her films and public appearances. Compare her 1955 radio interview to that of the Last Interview. with Richard Meryman. It may also be that in this particular interview Marilyn was more sombre than usual. The interview was about fame. At the moment, Marilyn was suspended by the studio. Meryman commented, “she looked great… but she was clearly troubled. I saw a lot of intensity, anger and sadness…she had that wild laugh, sort of a trademark but in the interview it seemed to come out at odd moments, out of place.”
When Marilyn rehearsed for her appearance at Madison Square Gardens she made her rendition of happy birthday for JFK breathier and sexier with each practice. A producer on the set didn’t like it and told her so. Afterward, Marilyn gave him the cold shoulder, turning her back on him whenever he approached.