MARY MARTIN, the star of so many Broadway musicals, once attributed her great success to her rapport with the audience. Neither her voice nor her appearance, she said, was anything special. But she had a confidence, a wide-open ebullience and an obvious joy in performance that captivated theater-goers and made them permanent fans. Hers was a charm for which she credited her home state: "If you're a Texan you just figure that everybody loves you."

Miss Martin, who died Saturday in California at the age of 76, personified the roles she played. If you are of a certain age, you will never hear anyone sing "My Heart Belongs to Daddy" without thinking of her and finding any other version wanting. Though countless others have played the role of Nellie Forbush in "South Pacific," Mary Martin will always be the one you imagine cavorting in an oversized sailor suit. She was the original Maria von Trapp in the Broadway production of "The Sound of Music," and she remains the eternal Peter Pan.

The spirit that audiences first saw more than 50 years ago did not seem to dim with age. In 1984, when she was already in her seventies and on the way to becoming a great-grandmother, Miss Martin agreed to play Peter Pan at a benefit concert in San Francisco. Wired and harnessed, she leapt from a box in the third balcony and flew over the audience singing as if she were 17 and, like Peter, would never grow old. And for those fortunate enough to have seen her perform and to have been won over by her sassy, joyful style, she never will.