It took some serious gumption to pull it off when Timothy Seelig, the charismatic artistic director and conductor of the San Francisco Gay Men’s Chorus, led his singers along with members of the Oakland Interfaith Gospel Choir on a “Lavender Pen” tour of five Southern states in 2017, a feat that the 2019 documentary“Gay Chorus Deep South”chronicled.

The Chronicle’sreviewcalled the film “emotionally satisfying,” stating that “beyond the stirring music … we witness the healing and enlightenment of chorus members, some of them bearing scars from their oppressive red-state upbringings.”

film is just one salient example of how Seelig advanced the foundational view that music and an LGBTQ mission are the co-equal “twins,” as he put it, of the 43-year-old ensemble. With Seelig at the helm, the Gay Men’s Chorus has brought newly commissioned works by such prominent composers as Stephen Schwartz, Jake Heggie, Andrew Lippa and Stephen Flaherty to audiences over the past decade.

“With unwavering artistic visions and standards, he has made the chorus one of the musical highlights in the city,” said Ragnar Bohlin, director of the San Francisco Symphony Chorus, in a statement.

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Now, after enlarging the ambitions and burnishing the sound of the ensemble for 10 years, Seelig, 70, has announced his retirement. He will lead a farewell 2021-22 season, beginning in September, and leave his post next July.

The board plans to embark on a search for his successor this August.

“Tim has been a driving force in the evolution of our movement,” said Robin L. Godfrey, executive director of the national support organization GALA Choruses, in a statement. Seelig’s “imprint on the LGBTQ choral movement,” added Godfrey, “will live on for generations.”

Lippa, a Broadway and classical composer whose mesmerizing “I Am Harvey Milk” received its premiere by the Gay Men’s Chorus in 2013, told The Chronicle that Seelig is “one of the greatest choral conductors in the country. He has this remarkable combination of musicality and personality.”

When Seelig first proposed a Harvey Milk project, he asked Lippa if he would like to contribute a five-minute piece to the evening. Lippa countered with a proposal to write a full-length piece of 50 minutes.

“Ultimately Tim came back and said they were in,” Lippa recalled. “His stance is, ‘What do you want to write, and do you want to write it for us?’ It’s every composer’s dream.”

“Harvey Milk” went on to performances at Lincoln Center in New York, the Walt Disney Concert Hall in Los Angeles and elsewhere. The recording was a hit.

“Tim kicked off a whole new creative vein in my career,” Lippa said.

Speaking by phone from the San Francisco International Airport last week, before boarding a flight to Denver to visit a friend and former chorus member, Seelig pointed to two accomplishments as high points of his tenure.

One, which he called “my greatest legacy,” was the creation of the Artist Portal at the AIDS Memorial Grove in Golden Gate Park, which took eight years to produce. Located on a vista point above the western end of the Grove, the Portal features an 8½-foot emperor chime. Seelig was determined to have an “aural component” to honor, among others, some 300 former chorus members who died as a result of AIDS.

A second point of pride is the purchase of a building at 170 Valencia St., which will double as a home for the chorus and a National Queer Arts Center.

“Tim has a passion for the mission,” said Chris Verdugo, the organization’s executive director, by phone. “He wants to make music with a purpose that touches and transforms the lives of the singers and the audience.”

Asked how Seelig achieves musical excellence with all-volunteer singers who rehearse once a week, Verdugo laughed and said, “Well, he demands perfection.”

Seelig was raised in the Southern Baptist Church and spent decades conducting both gay and straight choruses while teaching college students in Texas and elsewhere. He has written six books on choral music as well as a memoir, “Tale of Two Tims: Big Ol’ Baptist, Big Ol’ Gay.”

“One of the things I learned is that music is not an end in itself. It’s a means to an end,” he said. “In the Southern Baptist Church, music is used as a vehicle to move people’s hearts. I’ve tried to carry that idea over here.”

In his 2020 book, “The Perfect Blend,” a chapter titled “Connection or Perfection” questions whether one can have both. “That’s hard to achieve with a community-based choir with a wide level of musical abilities,” Seelig said. “It’s about taking people who don’t think they can achieve that and help them raise the bar. I’ve always wanted people there because they want to be there, to feel the community and the music.”

As for the suave, solid sound he’s inculcated in his decade with the Gay Men’s Chorus, Seelig traces it back to his own training as an opera singer.

“People tell me there’s a signature Tim Seelig sound,” he said. “If there is, it comes from my legitimate classical background.”

In addition to freelance conducting gigs, Seelig plans to spend time with family, including four granddaughters, in retirement. He may also do a second edition of his memoir, taking into account the challenges of the COVID era.

“About the worst thing you can do,” he said cheerily, “is release a memoir during a pandemic.”