NASHVILLE (Tennessee): The woman who gave Elvis Presley what she called the "woo-woo-woos" in holiday favourite "Blue Christmas" has been silenced. Mildred "Millie" Kirkham, 91, died on Sunday in Nashville, family members and collaborators said.

She is best known for her soaring background vocal stylings on numerous Nashville recordings by the likes of Elvis Presley, Roy Orbison, Patsy Cline and George Jones.

"Anytime they needed that high voice on something, she was always there," Scotty Moore, the guitarist for Presley early in his career, said on Tuesday.

Moore, who played on the 1957 "Blue Christmas" session, remembered Kirkham as not only a fine singer, but "a very nice lady."

"Everybody loved Millie," said A-Team session guitarist and Country Music Hall of Fame member Harold Bradley.

"I worked with her for a long, long time," he said. "She was a wonderful singer, but she was also a wonderful person and she always was smiling and never gave anybody any problems at all."

He also said that she did not mind sticking her neck out, which is what she did when coming up with the harmony on "Blue Christmas."

Gail Pollock, Moore's companion and a Nashville music business veteran, said her good friend "did not want to be remembered for being Elvis' woo-woo singer," but she was resigned to the fact that she would, indeed, be remembered for that little phrase she inserted during horseplay with Elvis and everyone else in the session.

Kirkham’s voice is an integral part of "The Nashville Sound," a more cosmopolitan form of country music that in large part was fashioned by Bradley, his producer and brother Owen Bradley as well as guitarist and producer Chet Atkins.

"Those vocals are some of the most instantly identifiable in the country and pop music history, said Peter Cooper, a writer and editor at the Country Music Hall of Fame and Museum in Nashville.

The cause of death was complications from a stroke last week, family members said.