A cellist when she was younger, Mary-Catherine Deibel managed a classical music group during her early years in the restaurant business, so it followed that she would draw a parallel between Greater Boston’s expanding culinary scene and its sprawling concert offerings.
“One thing I learned in the music business is that the more musical activity there is, the more people want to go to concerts, and that good concerts lead to more good concerts,” she told the Globe in 1984, a couple of years after opening UpStairs at the Pudding, which she co-owned.
And so it was with good restaurants, she said. Much like the conductors she watched while sneaking off to Friday symphony matinees, Ms. Deibel coaxed harmonious, ensemble performances every day — from the staff and patrons at UpStairs at the Pudding and its successor, UpStairs on the Square.
As co-owner of those Cambridge restaurants — both now gone, both missed by diners — she was a legendary presence at the front of each establishment, a hostess everyone remembered long after UpStairs on the Square closed at the end of 2013.
Ms. Deibel, whose longtime leadership roles in Cambridge business circles led many to consider her the unofficial mayor of Harvard Square, died Thursday in Beth Israel Deaconess Medical Center after a brief illness. She was 72 and lived in Arlington.
Recognizable to everyone, Ms. Deibel favored flowing scarves in magenta or pink, while co-owner Deborah Hughes sported ever-present oversized sunglasses. They were such a team that they often finished one another’s sentences in media interviews.
Each of their upscale venues — upstairs from Harvard University’s Hasty Pudding Club and upstairs on Winthrop Street — had unforgettable décor, the latter particularly zingy.
“In its glorious new incarnation, the renamed UpStairs on the Square could double for a stage set — especially if the production were a reimagining of ‘Alice in Wonderland’ by the ‘Moulin Rouge!’ director, Baz Luhrmann,” wrote Globe restaurant reviewers Joe Yonan and Amy Graves in 2002, after Ms. Deibel and Hughes moved UpStairs at the Pudding to Winthrop Street.
Over the years, patrons ranged from weekly regulars to luminaries such as chef Julia Child, cellist Yo-Yo Ma, and singer Bono of U2. The food was always a draw, as was Ms. Deibel.
“Every night in the restaurant was like a private dinner party at her home, where she was there at the door to greet you,” said David Waters, who formerly was general manager of UpStairs at the Pudding. “Even more than the food it was about the ambiance in the dining room she created, where you felt you were the most important person there.”
Georgia Murray, who met Ms. Deibel when they attended college together and invested in both restaurants, said her friend “just made you happy. When you walked in the door, she made you feel like you were the person she was waiting for.”
“Mary-Catherine had that generosity of spirit right up to the end,” Murray added. “She never lost her sense of humor and always wanted people to get together.”
Born in Arlington Heights, Ill., on Sept. 30, 1950, Mary-Catherine Deibel was the second of four siblings.
Her mother was Florence Baxter Deibel and her father, Robert Deibel, was an executive at companies including Oral-B toothbrushes and Teledyne Water Pik.
“We had a very traditional, 1950s, mom-at-home, dad-a-business-executive upbringing,” said Ms. Deibel’s sister, Margaret O’Connor of Dallas.
And yet, “Cathie always had a highly creative perspective on life and a sense of style,” her sister said. “Where our family was pretty down-to-earth, she always had a real flamboyance and a love for pretty things and sparkly things, and she was extremely witty.”
Ms. Deibel attended Catholic schools, graduating from Immaculate Heart Academy in Washington Township, N.J., and receiving a bachelor’s degree in English from Newton College of the Sacred Heart.
An aspiring writer, she began reading each issue of The New Yorker magazine as a teenager, and later received a master’s in English literature from Boston University. Ms. Deibel freelanced magazine articles and restaurant reviews, and wrote short stories, though she never realized her goal of publishing in her favorite magazine.
After college she launched two careers, managing the classical music group Banchetto Musicale, which became Boston Baroque, and working at the Peasant Stock restaurant along the Cambridge-Somerville line, where she met Hughes.
Ms. Deibel initially opened UpStairs at the Pudding in the early 1980s with Michael Silver, Hughes’s then-husband (they later divorced). Forced out of that location nearly 20 years later when Harvard bought the Hasty Pudding building, Hughes and Ms. Deibel reopened the restaurant in 2002 on Winthrop Street as UpStairs on the Square.
Through Ms. Deibel’s fondness for croquet she met Reid Fleming, a seven-time national croquet champion. She rode along when a friend picked Fleming up at the airport en route to a Newport, R.I., competition.
“They danced at the croquet ball and the rest is history,” Ms. Deibel’s sister said.
The couple married five years later, in 1992.
“She took a chance on me big time, but she never saw it that way,” said Fleming, a computer numerical control machinist. “She said, ‘I’ve got the love of my life. Let’s get married.’ "
Though he was shy, “she gave me confidence,” he said. “In any social circumstance, she knew exactly what to say and exactly what to do.”
After she and Hughes closed their restaurant in 2013, Ms. Deibel worked in development for Longy School of Music and then was director of development at the Cambridge Center for Adult Education. She also was president of the Harvard Square Business Association.
Over the years, her community work included, with Hughes, using the restaurant to help support Cambridge Cares About AIDS.
Ms. Deibel spent 15 years on the board of Community Servings, a Jamaica Plain nonprofit nutrition program for the critically and chronically ill, where Waters is chief executive, and which prepares about 1.2 million meals annually for people in Massachusetts and Rhode Island.
“Mary-Catherine used her limitless good will and can-do sunniness to make every event and occasion a festive pleasure,” wrote Corby Kummer, executive director of Food and Society at the Aspen Institute, in an e-mail.
“She and Deborah constantly cared for anyone who wanted to do good, and brought them together with a whole-face smile that could instantly lift anyone’s spirits,” said Kummer, who was among those who held wedding ceremonies at the UpStairs restaurants. “She made Upstairs an anchor of groups she realized needed to work together — a community-service organization with pink walls and Champagne.”
In addition to her husband and sister, Ms. Deibel leaves two brothers, Paul of Los Angeles and Robert of Denver.
A gathering to celebrate her life and work will be announced. “All Cathie wanted was a great party,” her sister said.
Ms. Deibel “probably had no idea how many people she touched and how many people are feeling the loss of that joie de vivre that she brought to us,” Waters said.
With Hughes, she also helped elevate Greater Boston’s status as a place to find inventive dining experiences and fine food.
“I think we’re a fabulous food city,” Ms. Deibel enthused in a Globe interview five years ago.
“I think in Boston, the diversity and the number of ambitious chefs is unparalleled,” she said. “How could it be better? I don’t know. Keep going. Maybe more food trucks!”
Bryan Marquard can be reached at firstname.lastname@example.org.