Hildegarde, 99, the cabaret sensation whose elegant piano and vocal style -- combined with flirty banter and a champagne smile -- made her an icon of nightclub sophistication for decades, died July 29 at a hospital in New York. The cause of death was undisclosed.

From vaudeville obscurity, Hildegarde became one of the highest-paid performers of the 1940s. Specializing in such wistful songs as Jerome Kern's "The Last Time I Saw Paris" and Noel Coward's "I'll See You Again," her substantial recording career, high-profile musical engagements and onstage charm brought her such nicknames as "The Incomparable Hildegarde" and the "First Lady of the Supper Clubs." The second came from another first lady, Eleanor Roosevelt.

Entertainer Bobby Short, a fixture at Manhattan's Cafe Carlyle, found Hildegarde's act "produced down to the last sigh, even to the blue spotlight that brought out the color in the red roses that invariably sat by her piano."

Few were flashier and more conspicuous about clothing than Hildegarde, although she noted a fondness for $6 shoes because "nobody can see them anyway." A Catholic, she gave her old gowns to poor priests to make vestments and once told an interviewer, "The brocade and velvet [ones] work best."

Much of Hildegarde's image and refinement had to do with her early manager, Anna Sosenko, with whom she formerly shared a 10-room apartment in Manhattan's Plaza Hotel, surrounded by masterpieces by Renoir, Manet and others.

Sosenko wrote Hildegarde's signature song, "Darling, Je Vous Aime Beaucoup," and tried to shroud the Wisconsin-born Hildegarde in publicity that lent her an exotic allure. She planted stories in the media about such implausibilities as an elderly Swedish monarch going gaga for her.

A noted flirt, Hildegarde wore long, white gloves ("Miss Piggy stole the gloves idea from me," she once said), and told risque anecdotes while parceling out long-stemmed roses to men in her audience.

During a performance in Washington, she nestled up to a dour-looking Sen. John L. McClellan (D-Ark.) and waltzed with him while she whispered for all to hear, "Oh, Senator, you're entrancing. . . . You dance so beautifully. . . . Darling, you're terrific. . . . Why go back to the Senate. . . . And where's your wife?"

Wise investments and work as a pitchwoman for a bottled water company, barley vitamins and bathtub device called the PercussOwhirl provided her with a comfortable income through the rock-and-roll era.

The daughter of German immigrants, Hildegarde Loretta Sell was born Feb. 1, 1906, in Adell, Wis., and raised in Milwaukee. She played piano for silent film showings to pay her way through Marquette University's music school.

She hoped to be a concert pianist but in 1926 saw an act at a Milwaukee theater called Jerry and Her Baby Grands, featuring four women playing four baby grand pianos. "I was overwhelmed and visualized that I would be one of them," she told an interviewer. To get the attention of the act, she banged out a hot rendition of "The 12th Street Rag," the tune that she later said "got me into show business and out of Milwaukee."

While staying at a boarding house in Camden, N.J., she met Sosenko, an aspiring songwriter and the daughter of the owner. With a handshake, they formed a business partnership that lasted two decades. Their friendship dissolved amid circumstances that never were made clear publicly.

Early on, Hildegarde was a song plugger for Irving Berlin in New York. Hoping for better prospects, she and Sosenko went to Europe in 1933, and Hildegarde worked at the Cafe de Paris, a chic supper club where Broadway star Marion Harris was the headliner.

"I was dreadful, down the bill," Hildegarde later said. The man who ran Cafe de Paris "was very nice and said that it was a matter of learning more, so Anna and I went to Paris where we thought we could learn the art of cabaret."

Meanwhile, Sosenko said she "equipped myself with the biographies of the truly great artists in the theater. I absorbed the careers of Bernhardt, Duse, Anna Held and Flo Ziegfeld like a sponge. . . . I learned that illusion was an integral part of show business."

Sosenko crafted Hildegarde's transformation in appearance and reputation. They sacrificed a month's wages to pay for Hildegarde's wardrobe makeover. Hildegarde also honed her act in Paris and refined her singing voice in French, Russian, Italian and Swedish to give her the allure of an international woman of mystery. They considered it a coup when nightclub reviewers were unable to tell whether she was an American with a French accent or French with an American accent.

Finding American nightclub audiences rowdier than European ones, she mastered the use of dramatic lighting and such tricks as dancing with diners and kidding men in the audience. This charmed many, but one dissenting critic remarked that she "wears long gloves at the piano merely because she cannot play enough to keep herself warm."

Hildegarde's warm voice was especially suited to such wartime favorites as "I'll Be Seeing You" and the English-language version of "Lili Marlene." She spent most of the 1940s on the NBC Radio program "Raleigh Room," sponsored by the cigarette company. Her annual salary reportedly was $150,000.

As musical tastes changed, she returned to dinner clubs and touring stage shows. Through a rigorous beauty and exercise regimen, she remained an energetic presence on stage through the 1990s.

She once described herself as "an incurable romantic. . . . I traveled all my life, met a lot of men, had a lot of romances, but it never worked out. It was always, 'Hello and goodbye.' "

She leaves no immediate survivors.

Hildegarde was one of the highest-paid entertainers of the 1940s. Eleanor Roosevelt dubbed her "First Lady of the Supper Clubs."