After his retirement in August 2015, John Oliver was looking forward to writing three books, including a memoir and a Southern Gothic novel, and tending his beloved greenhouses and gardens at his year-round 1880s country home on a rural byway in the pastoral town of Alford.

Oliver, who founded the Tanglewood Festival Chorus for the Boston Symphony in 1970 and directed it until his retirement, told The Eagle's classical music writer, Andrew Pincus, at the time that he would miss his "family," the choristers who revered and sometimes feared him.

He had conducted at least 200 works in an estimated 1,000 BSO performances at Tanglewood and in Boston's Symphony Hall.

"Life is going to slow down," he said, marveling at his hectic list of commitments at the BSO and beyond when he was 40. "I don't know who that person was. He had a lot of energy."

Sadly for his many friends, admirers and former colleagues, the retirement he so keenly anticipated was cut short by an extended illness, which took his life Wednesday night at Fairview Hospital in Great Barrington.

Oliver, a native of Teaneck, N.J., was 78.

In what was one of his final interviews, he told Pincus that when he was invited to form a chorus for the BSO, he chose the name Tanglewood Festival Chorus "because I did not want to see in print 'The Boston Symphony Orchestra and Chorus.'"

The current roster numbers close to 300; about 100 sing in a typical performance on a rotating basis. At least one of the original 1970 members still sings with the chorus.

Behind the scenes, Oliver would prepare the chorus and then sit in the audience for the performances led by other conductors. At Tanglewood, often the longest, loudest ovations would ring out for the chorus and Oliver.

In an interview 12 years ago, he recalled how Leonard Bernstein, "who was very exacting," attended multiple choral rehearsals of Mahler's "Resurrection Symphony" at Tanglewood in 1970. After urging the singers' entrance to be as soft as possible, barely perceptible, "he stood there listening, smoking throughout," Oliver recalled. "Finally, Bernstein said `I'll buy that,' and off he went into the afternoon."

"Few people in the 137-year history of the Boston Symphony Orchestra dedicated so many years of their creative lives to the orchestra as John Oliver during his 45-year tenure," BSO Managing Director Mark Volpe said in a prepared statement. "All of us at the BSO are very grateful to John for his steadfast commitment to his vision in founding the TFC and nurturing it through decades of acclaimed performances" at Tanglewood, in Boston and on international tours.

Upon his retirement, Oliver was awarded the BSO's second Tanglewood Medal (the first went to Seiji Ozawa), and he received the newly created lifetime title of founder and conductor laureate of the chorus. In 2016 and 2017, he held the Tanglewood Music Center's Donald and Laurie Peck Master Teacher Chair.

In a 2006 interview, chorus singer Betsy Bobo of Otis described Oliver as "the consummate musician. He has a way of getting exactly what he wants from people ... an endless reserve of ways of talking to you, and to conduct so that he communicates the precision and the detail. There's not a time that I don't feel fortunate and grateful."

After attending the University of Notre Dame and the New England Conservatory of Music, Oliver began working with the Boston Symphony in 1964, preparing a community boys' choir for Alban Berg's opera, "Wozzeck," led by the orchestra's music director, Erich Leinsdorf.

In 1966, he rehearsed a youth choir for the BSO's performances and recording of Mahler's Symphony No. 3, also with Leinsdorf, leading to his appointment as assistant for the choral and vocal music program at the Tanglewood Music Center summer institute, then called the Berkshire Music Center.

He was named director of vocal and choral activities at the music center and founded the Tanglewood Festival Chorus in 1970, working with Bernstein on Beethoven's Ninth Symphony, and later with music directors Ozawa and James Levine, with Boston Pops conductors John Williams and Keith Lockhart, as well as with numerous guest conductors.

Oliver's impact extended beyond his work with the chorus. He led his own John Oliver Chorale and taught at the Massachusetts Institute of Technology for 32 years. He also was a faculty member and choral director at Boston University.

"John Oliver's dedication to forming and then leading the Tanglewood Festival Chorus for 45 years represents an extraordinary commitment to the Boston Symphony Orchestra and to the art of choral singing," said BSO Music Director Andris Nelsons. "Our hearts go out to all who loved and respected John, including his many fans throughout the BSO family and beyond in the music world at large."

On the final August weekend of the 2015 Tanglewood season, Oliver prepared the chorus for Nelsons' performance of Mahler's Symphony No. 8, composed for monumental forces of orchestra players and singers, and for the traditional closing performance, led by guest conductor Asher Fisch, of Beethoven's Ninth Symphony and its paean to brotherhood, the "Ode to Joy."

"John's work with the chorus and the BSO over many decades will always be an important part of the orchestra's great legacy and its mission to realize the very best in the classical music art form," Nelsons said in his prepared statement.

A private service is planned for Oliver this week, according to the BSO, which listed his survivors as his cousins Helene Carskaddin, Janet Domerski, Lyn Neandross, Jerilyn Simpson and Nancy Sorge, as well as his dear friends Joel Evans, James Soules and Anthony St. George.

A concert to celebrate his life will be held this summer, during the Tanglewood season. Donations in his memory can be made to the Boston Symphony Orchestra's Tanglewood Festival Chorus Fund.

Clarence Fanto can be reached at cfanto@yahoo.com or 413-637-2551.