TORONTO (AP) — U2 singer Bono, guitarist The Edge and their band mates have let their guard down for a revealing documentary about their creative development and a pivotal career shift 20 years ago.

“From the Sky Down” opened the Toronto International Film Festival on Thursday night, the first time in its 36-year history that the prestigious cinema showcase began with a documentary. The film centers on the band’s renewed sense of purpose as they created the 1991 album “Achtung Baby.”

The Edge and Bono joined director Davis Guggenheim for two screenings of the film, which premieres on Showtime in October.

“We’re very, very protective of our privacy, and especially, our creative process,” Bono told the crowd before the first screening. “Not because we’re that precious, which we are. But more because of that old adage, if you knew what went into the sausage, you wouldn’t eat the sausage.”

Director Guggenheim’s previous credits include the Academy Award-winning “An Inconvenient Truth,” about Al Gore’s global-warming campaign, and “It Might Get Loud,” the guitar dream-team matchup of The Edge, Led Zeppelin’s Jimmy Page and Jack White of the White Stripes.

The film blends new interviews with archival footage of the Irish rockers in their early days after forming in the mid-1970s.