A song stylist compared to Frank Sinatra and Nat King Cole, and whose life's travails sometimes seemed at odds with her professional survival, she was surrounded by family in her Beverly Hills, Calif., home when she died.
She had undergone lung surgery at the Mayo Clinic in Minnesota in January and doctors afterward, her friends said, had declared the operation a success and said she could look forward to resuming her singing appearances.
A new diagnosis "came very suddenly less than a month ago," her partner in more than 200 performances, Michael Feinstein, told United Press International early Sunday.
"At that point she realized she wasn't going to sing again and very quickly made peace with the fact she was going to be leaving soon," he said.
"I will miss her the rest of my life," he said. "She was just a delicious human being."
Her voice, Feinstein said, "communicates the same way that Nat Cole's voice communicated, or Sinatra. You knew a lot about who she was as a person when you hear that sound. It was honest and it was compelling and it was all from the heart."
Feinstein was reached in Cincinnati, Ohio, where he was performing near her home town of Maysville, Ky.. As it happened, her brother, television personality Nick Clooney, was with him at the show. "It was one of those strange moments. We were all together," he said.
Her five children, grandchildren and her husband, Dante DiPaolo, were with her at the end, Clooney's publicist, Linda Dozoretz, told UPI.
"She was very self deprecating and it was genuine," Feinstein said. "She loved talent. She was a great mentor and support of others and she lived passionately."
Feinstein continued, "She deserves to be remembered for the great artist that she was and I'm in shock, because she's one of those people I never expected to lose in spite for her physical difficulties."
Her recordings, he said, "will remain an aural legacy and a primer for other singers when they want to know how it should be done."
Rosemary Clooney, he said, "was one of the great distinctive voices of the century. She was an impeccable interpreter of the best of our American musical literature."
A web page that presents her music and her life story from her first overnight hit recording, "Come-on-a-My-House," to her movie appearances, including with Bing Crosby in "White Christmas," and her later life, is on the Internet at rosemaryclooney.com.
She wrote a book, "This for Remembrance," published in 1978 about her recovery from a nervous breakdown triggered in part by her divorce from movie actor Jose Ferrer.
Coming to terms with the divorce and an addiction to tranquilizers, she was campaigning for her friend Robert Kennedy when he was assassinated. "A long and painful journey through therapy" ensued, wrote Clive Davis a year ago in The Times of London as she performed with Feinstein at Festival Hall.
"Over the past quarter century, she has turned out roughly an album a year," Davis wrote. "There is a garishly melodramatic quality to her rise and fall that comes straight out of a Jacqueline Susann potboiler."
She socialized in London "with Gielgud and Olivier," he wrote, but that pregnant in a failing marriage, she communicated an unease that writer Ira Levin, after a visit, seemed to reflect in his later best seller, the horror classic "Rosemary's Baby," turned into a Roman Polanksi film.
The long trip from young singer and starlet "bridged an incredible era of music in that she started as one of those many pop singers and ended up being the elder statement of all singers," Feinstein said.
"She did not like the material she had to sing when she started recording as a solo artist for Columbia," continued, "but it was those flash-in-the-pan hits that made people aware of her talent -- and her talent transcended the material."
That single, "Come-on-a-My-House," was a catchy number written by Ross Bagdasarian who, later, as David Seville, created the Chipmunks. It became an overnight hit song.
She also enjoyed best-selling hits with "Tenderly," "Hey There" and "This Old House."
Born May 23, 1928, in Maysville, she began singing while in grammar school. She and her sister Betty had a radio program in nearby Cincinnati when she was only 13.
In 1945 Rosemary and Betty became singers in Tony Pastor's dance band, going on to tour with Pastor until 1949 when Rosemary branched off as a solo act and recorded her first hit.
Her healthy, girl-next-door appearance helped her win a movie contract, with her most seen Hollywood role the one in "White Christmas with crooner Bing Crosby" She also starred in "The Stars are Singing," "Here Come the Girls," "Red Garters" and "Deep in My Heart" with then husband Ferrer.
She wrestled with the divorce and an audience that became riveted on rock and roll, assuming she would forever more be out of fashion.
But she made a recovery beginning in the 1970s, following a guest appearance with Crosby, emerging again as a recording star and concert artist.
In December, 1982, Rosemary joined Tony Bennett and Count Basie at the Westbury Music Fair.
At the end of that week CBS-TV showed a special television movie based on her life called "Rosie," and starring Sandra Locke.
Even at that point her career was far from over. In October last year, San Francisco Chronicle reviewer Phil Elwood wrote that the crowd "rose, applauded, whistled and shouted" as she addressed the audience at the San Francisco Jazz Festival.
In September, Sherry Crawford of the Evansville Indiana Courier & Press wrote, "And then it happened -- a legend walked on stage, sat down on a stool and reached out to the audience the way few entertainers ever do. Rosemary Clooney is a sassy, feisty, fund and more important, she is so down-to-earth."
"There was no difference being with her on stage or off," Feinstein said Sunday. "She was the same warm funny charming lady. She loved life and she loved singing more than anything."
In poor health before her January surgery, "It was the love of her audience that sustained her when she wasn't in the greatest physical health these last couple of years," he said. "She still insisted on getting out there and performing because it was just part of her soul."
Davis, in his Times of London piece last June, also wrote, "Her face is still handsome. Catch her in profile and you can immediately see the shadow of her nephew, George Clooney."
Young George, he continued, "used to stay at Rosemary's house in Beverly Hills. Now, he is famous and his aunt watches him hurtle through the same dizzying trajectory that she knew as a young woman."
"She was probably hoping to be well enough to sing at the Rosemary Clooney Festival in her home town this fall," Feinstein said. "Also James Taylor had requested she sing for him at an event at which he was being honored. She adored him.
"It seemed to be that that could possibly give her the impetus to get it together and sing again, in that she was still recovering, slowly but surely," he said.
"She had the gift of the music. Music was something that was a constant for her, when a lot of other things came and went," Feinstein said.
(Reporting by Denny Gulino in Washington)