Dorothy Sarnoff, an actress who made an impression on Broadway and in opera before embarking on an influential career as an image consultant, died Dec. 20, 2008, at her home in Manhattan. She was 94. To Broadway audiences, Ms. Sarnoff was Mrs. Thiang, the chief wife to the King of Siam, in the original production of The King and I, and the first actress to sing "Something Wonderful." To opera fans, the Brooklyn-born performer was Miss Pinkerton in the world premiere of Gian Carlo Menotti's one-act radio opera The Old Man and the Thief, and, as a member of the New Opera Company, the star of a long, early 1940s Broadway run of Rosalinda, an English-language version of Johann Strauss' Die Fledermaus. She also sang in Tosca and Faust on Broadway.

In the mid-sixties, however, with her stage career dimming, she began to conduct vocal coaching classes designed to aid women in how they verbally presented themselves. The six-class course was first called Speech Cosmetics, and then — as it became more popular and increased in scope — Speech Dynamics. Ms. Sarnoff went on to coach businessmen, corporate heads and politicians such as Jimmy Carter, Menachem Begin, Bob Dole and Warren Christopher. Her ethos was that everyone could become a relaxed and commanding speaker if they could only isolate and accentuate their strengths and dispel their weaknesses. She instructed her clients to project "the vibe of joy," "the vibe of concern" and "the vibe of authority" when speaking in public. One of her maxims was "Make sure you have finished speaking before your audience has finished listening."

Ms. Sarnoff, who is credited with being a forerunner in the self-help movement that flowered in the 1980s and '90s, published several best-selling books, including "Speech Can Change Your Life," "Make the Most of Your Best" and "Never Be Nervous Again."

One of the keys to her teaching was learned from her The King and I co-star Yul Brynner. The actor tensed his abdominal muscles to rid himself of nervousness. Ms. Sarnoff translated this into an abdominal exercise called the Sarnoff Squeeze, a technique she passed on to her students.