“Very few people outside the art world knew about him,” confided Olivier Meslay, the director of the Clark Art Institute in Williamstown, Mass.

When it was announced last month that Aso O. Tavitian, through his foundation, had left the Clark 331 artworks estimated to be worth hundreds of millions of dollars — plus $45 million to build a new wing to house it all — the news prompted some to wonder: So who was this guy?

Tavitian, who died in 2020 at age 80, was a self-made man and a focused, under-the-radar collector who built a staggering trove of old masters and other classical European artworks — by esteemed painters like Hans Memling, Peter Paul Rubens, Parmigianino, Elisabeth Louise Vigée Le Brun and Gian Lorenzo Bernini — in just 16 years.

Most of the objects that Tavitian collected that were not in the Clark gift — including fine English furnishings that resided in his grand houses, one in New York City and one in Stockbridge, Mass. — will be sold in a four-part auction at Sotheby’s New York in February, “The Vision of Aso O. Tavitian,” with an overall estimate of $14 million to $24 million.

It will finally give the public a window into his art-filled and very well-appointed life.

The collection had an aristocratic cast — Meslay called it “princely.” Some notable lots include a religious painting by the Renaissance master Ambrosius Benson (estimated at $600,000 to $800,000) and a Madonna and Children from around 1620 by the Italian old master Daniele Crespi ($300,000 to $500,000). But Tavitian, while a lover of fine wine, especially Burgundy, was not born to the manor.

He was a Bulgarian-born Armenian (the name Aso, which he preferred, was short for Assadour) who grew up poor and fled Communism with his family in 1959, moving to Beirut.

“Times were hard for his family, and they went to Beirut with no money and no place to live,” said his partner, Isabella Meisinger, who was with him through his primary collecting years, after 2004.

“Catholic teachers helped him with his education, and he tried to help other people in return,” Meisinger said. The Tavitian foundation, which will receive the proceeds of the Sotheby’s sale, focuses its philanthropy on education and peace, particularly in the Armenian region, and on the arts.

Tavitian immigrated to the United States in 1961, when he was around 21, and drove a taxi while studying at Columbia University. Later in life, that experience showed. “He drove the taxi driver way — weaving in and out and trying to get ahead of the traffic,” said his longtime employee Laura Fitzpatrick, who is the director of operations for the Assadour O. Tavitian Trust.

At Columbia, Tavitian received a master’s degree in nuclear engineering and worked on a Ph.D. in nuclear physics, but he did not complete his dissertation. In 1969, he was a co-founder of what became the software sorting company Syncsort, later becoming its chief executive and a majority shareholder.

In 2004, a notable year in several ways, he moved into a grand townhouse on the Upper East Side that had been under renovation for five years.

By that time he was 64 and a widower — his wife, Arlene, had died in 2002 — and he met Meisinger on a trip to the Hamptons, where she was working in an antiques shop.

“In the beginning, he thought he would just decorate the houses,” said Meisinger, who recalled that most mornings, they would pore over auction catalogs of paintings and sculptures at the breakfast table. “It took him some time to go from the $400,000 range into the millions.”

But when the leap happened, “It became an explosion of buying,” said David Bull, a painting conservator who advised Tavitian on purchases.

Etienne Bréton, a Paris-based consultant and dealer who worked with Tavitian locating pictures like Jean-Antoine Watteau’s “The Proud Man” (circa 1715), one of the paintings in the Clark gift, said that the speed of Tavitian’s progress was unusual.

In the case of Watteau, Bréton found the work in a collection in southwest France and personally ferried the consignment on the Eurostar to Tavitian’s suite at Claridge’s hotel in London for a viewing. Tavitian agreed to pay around $3 million for it.

Tavitian’s prime collecting years came as the art world turned most of its energy to contemporary art, leaving relative bargains available. Bréton said it “amused” Tavitian when he saw freshly painted works going for tens of millions, saying of his old master purchases, “This is nothing compared to that.”

Ignoring trends helped fuel the quest. “I can’t give you another example post-1970 of anyone who put together a collection of old masters like that,” Bréton said.

Tavitian’s taste ran heavily to portraits, from roughly 1450 to 1850. Bréton echoed others in Tavitian’s life when he noted that the collector imbued “a human personality” to the painted faces he surrounded himself with, and that the sheer skill of old master artists for bringing their subjects to life may help explain his devotion to the genre. “He never had children, so these were his babies,” Meisinger said.

Meslay, the Clark’s director, recalled Tavitian going on about the power of a marble bust by Jean-Antoine Houdon, “Little Lise” (1775), on which he spent more than $2 million, giving it to the Clark. ”He was speaking of it like it was alive,” Meslay said.

Meisinger said it was the delicacy of the ribbon in Lise’s hair and her angelic face that helped seal the deal. She added that it was Tavitian’s 2006 purchase, for more than $5 million, of Parmigianino’s “Portrait of a Man” (1530)— a cornerstone of the Clark gift and a highlight of what will be the Aso O. Tavitian Wing there, being designed by Selldorf Architects — that put him in the stratosphere.

He started to go for “the best of the best,” she said.

An increase in purchasing power didn’t hurt. In 2008, he sold a large portion of his stake in Syncsort.

Each fall, Tavitian and Meisinger would host a dealers’ dinner at their East 79th Street home, amid the English and French antiques, where advisers would bring works for him to consider.

Not that he was a soft touch on price. “If he was interested, he’d take a day or two to think and then he’d make an offer,” said Bréton. “He’d say, ‘When I make an offer, I won’t move from it. You take it, or you don’t take it.’”

George Wachter, the worldwide co-chairman of old master paintings at Sotheby’s, agreed that the collector “didn’t want to bargain.”

At the same time, he could be dogged in pursuit of the right work, especially at auction. Wachter recalled, “He said to me once. ‘When I decide I’m bidding on something, it’s mine already.’”

Tavitian thought nothing of flying to Paris for a day to look at a painting, or to London to look at a Georgian bookcase.

The London-based English furniture dealer Simon Phillips, of Ronald Phillips Ltd., said he saw “some old friends” among the furniture pieces that will go on the block at Sotheby’s — meaning items he sold to the collector, including a pair of late George II carved mahogany library armchairs, circa 1755, originally made for Eccleshall Castle in Staffordshire, England, and covered in elaborate French needlework, estimated at $150,000 to $250,000 for the pair.

Phillips said that Tavitian took care of his treasures, too. “He always said that the sunlight was tough on the furniture at his house in the Berkshires,” Phillips said, noting that he kept the finest pieces in the city. “He wouldn’t put something great in the window.”

Meisinger knew more about furniture than paintings when she met Tavitian, but learned about other fields along the way. She urged Tavitian to take a second look at Gian Lorenzo Bernini’s Renaissance bronze “Countess Matilda of Canossa” (circa 1630-39) when they saw it at an art fair in Maastricht, the Netherlands. As a child she had seen Bernini’s great Fountain of the Four Rivers in Rome, and it made an impression.

“He said, ‘That’s a lot of money,’” Meisinger recalled. “I said, ‘If you don’t buy it, someone will grab it right away. A small one by Bernini is rare.’”

They went to lunch and discussed it for about 90 minutes, and Meisinger recalled that Tavitian ended up paying just under $2 million for the piece, which Clark visitors will be enjoying in a few years. It is one example of the valuable sculptures that bolster the medium’s prominence at the museum, not previously one of its strong suits.

Tavitian loved the Clark, which is only about 35 miles from Stockbridge. He joined its board of trustees in 2006 and showed some of his works in a 2011 show, “Eye to Eye: European Portraits, 1450-1850.”

Tavitian was involved with other institutions, too, serving on the board of the Frick Collection for 12 years. He left the Frick and the Metropolitan Museum of Art one major work each: Giovanni Battista Moroni’s “Portrait of a Woman” (circa 1775) and Francesco Salviati’s “Bindo Altoviti” (circa 1545).

In the fall of 2019, he got a cancer diagnosis. He had already been considering the Clark gift but after the health news, “That accelerated his plan,” Fitzpatrick, his assistant, said.

But he did not imagine that he had only six months left. “He thought he had five years to live,” Meisinger said.

When Covid hit in March 2020, the couple decamped to the Berkshires, and Tavitian died of septic shock in the hospital there, though the cancer was far along, too, said Fitzpatrick.

Meisinger and Tavitian had planned to be married, but in the early days of the pandemic, they couldn’t find anyone to perform the ceremony before he died.

“I tried to get a license to marry them in Massachusetts, but it came the day after he died,” Beinecke said.

Tavitian told Meisinger that after his death, she would have her pick of artworks that were not in the Clark donation.

She chose a handful of pieces, including Johann Wilhelm Preyer’s “Still Life of Grapes” (1831-36), because it hung in the kitchen and reminded her of his interest in wine.

That bequest may have been smaller than the one to the Clark, but it demonstrated the collector’s faith in art’s power to endure.

Bréton said Tavitian’s attitude was: “I will die, the dealer will die and the auction rooms will change. But the picture will remain.”