At six feet tall and a little more than one foot wide, Harry Bertoia’s Sounding Sculpture is nearly the size of the average American male, but the piece still maintains a dramatic presence. With its neat, parallel rows of individual nickel alloy spires jutting out of its square base, the static structure can appear to be growing in real time. Furthermore, as is the case with many of Bertoia’s sculpture work, Sounding Sculpture is interactive, producing a unique tone that was painstakingly honed in the late Italian-American artist’s Pennsylvania recording studio.

When Maria Cox lent the piece to the Museum of Contemporary Art Jacksonville some years ago, it was a big hit (especially when its auditory capabilities were put on display by a gloved docent). It’s part of Maria’s and her late husband Donald’s personal collection, and one can easily imagine Sounding Sculpture serving as a source of late-night entertainment for modern-art-appreciating guests in the Coxes’ home.

Now Bertoia’s sculpture, along with 49 other artworks representing the Coxes’ eclectic tastes and ambitious curatorial spirit are set to become a part of MOCA’s permanent collection. Included in the Coxes’ recent gift are two paintings by abstract and neo-expressionist painter Philip Guston (including 1969’s Book), pop-artist Keith Haring’s Two Dancing Figures sculpture, and abstract-expressionist Joan Mitchell’s painting, Chord III. The donation — which is valued at more than $5.8 million — comes just 12 years after the Coxes’ 2004 gift of 48 works, which have since become staples of MOCA’s permanent collection.

The Coxes began collecting while living in New York City during the artistically fertile 1970s, actively seeking out works by Mitchell, Guston, Shapiro, Frank Stella, Haring, Malcom Morley, Jasper Johns, and many more.

Donald, who died in 2006, was at one point a senior vice president at Exxon. After retirement, he served as president and trustee of the American Federation of Arts, a trustee of the American Academy in Rome, a member of the Whitney Print Committee, and emeritus trustee at Polytechnic Institute of New York University and Bluefield College in Virginia.

Maria, after graduating from Cornell, worked in interior design for firms in San Francisco and Boston before starting her own firm in New York City. Her work led to collaborations with prominent architects; she lent her skills to designs at Lincoln Center’s Opera House and Avery Fisher Hall (now David Geffen Hall).

“We saw an enormous amount of art galleries, museums, studios, in New York and traveling,” Maria Cox said in a press release provided by MOCA. “In New York, sometimes on a Saturday, we might have visited up to 28 galleries. There was so much going on in the galleries and museums uptown, midtown, SoHo, and then Tribeca and further east and south.”

The liveliness of the ’70s New York art scene as well as the couple’s broad tastes are certainly evident in the nearly 100 pieces that have been donated to MOCA. The newest donation includes works collected from New York to Paris and beyond. “Don and I mostly agreed on selections,” Cox said. “If we didn’t agree, we didn’t buy it.”

“They’ve added such depth and diversity to the collection,” says MOCA Director Ben Thompson. “They didn’t just collect one kind of art. Included in this donation are pop art, there’s gestural abstraction, figurative work, sculpture, painting, works on paper … I think it represents the individual interests of both Maria and Donald, as well as their common interests.”

Maria Cox has been MOCA’s longest standing donor, building a relationship spanning 12 years that has turned out to be crucial to the institution’s reputation and long-term viability.

“Over the years, Maria has supported us in very integral ways,” says Thompson. “This donation is Cox’s most significant contribution to the museum to date. In terms of the quality and scope of the works, it is a transformative gift.”

MOCA plans to exhibit a selection of the new objects in “Breaking Ground: The Donald and Maria Cox Collection,” which runs from Sept. 24 through Jan. 8.