Her friends at the music school often said that the C in her name stood for Conservatory, not her middle name, Catherine.
Born in Baltimore, she was the daughter of William W. Walker and Mary Catherine Shafer Walker. Her mother's family had a pork packing business near the Lexington Market.
Miss Walker was a 1929 graduate of Western High School. She came from a musical family and spent her summers at a family home, the Lilacs, on Reisterstown Road at Fords Lane, where she heard an uncle play the violin. She could recall waving the American flag at World War I soldiers marching past. She often spoke of her father's Model T Ford.
She attended the Peabody Preparatory School and later studied piano with Elizabeth Coulson and voice with Frazer Gange at the conservatory. She graduated from Peabody in 1934 and initially taught piano and did secretarial work for a steamship line.
She returned to Peabody in 1942 to become what was officially known as a secretary in the conservatory office. Friends said that title was deceptive because she accomplished much more.
Jeffrey Sharkey, director of Peabody Institute, said, "I had the pleasure of celebrating Mary's birthday with her a few years ago. She was delightful, full of energy and proud of her years at Peabody. We had a great conversation catching her up on the latest gossip and sharing memories of her time at Peabody."
In 1967, after 25 years in the conservatory office, she was appointed as the first director of Alumni Relations. She retired in 1976, after 34 years of service to Peabody.
Reginald Stewart, director of the conservatory from 1941 to 1958, said in a letter read at her retirement party, "Mary ran the school and for that I always will be grateful."
Lynn Hebden, the retired dean of the Peabody Preparatory School and former alumni director, said that when those words were read, Miss Walker was shocked that he would say such things. "She was extremely modest. I don't think she ever realized what influence she had on so many people. She was the sanity at Peabody," she said.
Friends said that Miss Walker had a sympathetic ear for students and faculty members who listed their troubles.
"She was also at the school after World War II when students were returning from military service. They were older and had their own set of issues. Mary kept the even keel," said Ms. Hebden.
Robert O. Pierce, a former Peabody director who lives in Towson, recalled his first day at the school in 1958.
"She was a person of devotion and energy," he said. "Any institution should value people like her and be on their knees to have such people. She was invaluable. She was perfectly easy to work with and never put her own agenda first."
At her 1976 retirement dinner, she was honored by her colleagues for her "knowledge, ability, understanding and sincerity, as well as for her famous wit and charm."
In 1982, the Johns Hopkins University Alumni Association presented her with its Heritage Award.
At her 90th birthday in 2001, more than 170 gifts were made in her honor to refurbish seats at the Friedberg Concert Hall at Peabody.
After leaving Peabody, Miss Walker became a volunteer driver for Meals on Wheels of Central Maryland. She drove a Buick into her late 80s.
In addition to her Peabody activities, she was a longtime member of Brown Memorial Presbyterian Church on Park Avenue. She sang in the choir under the direction of organists Virgil Fox and Richard Ross, who were friends and Peabody faculty members.
After moving to the Edenwald Retirement Community, she became its music chairman and arranged music programs.
A memorial service is being planned for January at Brown Memorial Presbyterian Church.
She is survived by 10 cousins.