Bruce Springsteen performed a secret concert for President Barack Obama and his staff as they leave the White House, urging optimism in uncertain times, the rock legend's fanzine reported.

Backstreets, a long-running magazine and website that methodically documents Springsteen's shows, said The Boss played a 15-song acoustic set in the White House's East Room on January 12.

The fanzine, quoting an anonymous "longtime Backstreets reader" in attendance, said Obama and First Lady Michelle both attended but otherwise the crowd consisted of 200-250 mostly low-profile administration staffers.

The mood at the concert and a related reception "was not exactly somber, but it wasn't festive, either. It was elegiac, I'd say," the witness wrote.

"There was a clear sense of something ending, both with the conclusion of an adventure for the staff and the silent presence of the coming political transition," the person wrote, referring to Donald Trump taking power Friday.

Performing his 2007 song "Long Walk Home," Springsteen spoke "about being in a difficult moment and maintaining optimism," the attendee wrote.

The fanzine said Springsteen sang two songs with his wife Patti Scialfa, who is a member of his E Street Band, and performed his classic "Born in the U.S.A.," telling the crowd how the ode to working-class struggles was so often misunderstood politically.

Springsteen, who has been more overtly political in the past decade, campaigned for defeated candidate Hillary Clinton, telling a giant election-eve rally in Philadelphia that Trump had a "profound lack of decency."

The fanzine writer said the White House concert stood apart among Springsteen concerts.

"It was a humble, quiet gesture from Bruce to say thanks to President Obama, the staff and their families. No pomp, no ceremony, no press. Just the man, the guitar and the songs," the writer said.