LONDON — “ABBA Voyage” is certainly a trip.

Four decades after the Swedish pop supergroup last performed live, audiences can once again see ABBA onstage in an innovative digital concert where past and future collide.

The show opens to the public in London on Friday, the day after a red-carpet premiere attended by superfans, celebrities and Sweden’s King Carl XVI Gustaf and Queen Silvia. The guests of honor were pop royalty — the four members of ABBA, appearing in public together for the first time in years.

They were in the audience, though. Onstage at the specially built 3,000-seat ABBA Arena next to east London’s Olympic Park were a 10-piece live backing band and a digital ABBA, created using motion capture and other technology by Industrial Light and Magic, the special effects firm founded by “Star Wars” director George Lucas.

The voices and movements are the real Agnetha Faltskog, Björn Ulvaeus, Benny Andersson and Anni-Frid Lyngstad — choreographed by Britain’s Wayne McGregor — but the performers onstage are digital avatars, inevitably dubbed “ABBA-tars.” In unsettlingly realistic detail, they depict the band members as they looked in their 1970s heyday — beards on the men, flowing locks on the women, velour pantsuits all around.

The result is both high tech and high camp, a glittery supernova of stupefying technology, 1970s nostalgia and pop music genius.

For many in the audience, it was almost like being taken back in time to watch ABBA perform classics including “Mamma Mia,” “Knowing Me, Knowing You,” “SOS” and “Dancing Queen.” The peppy 90-minute set also includes tracks from “Voyage,” the reunion album the band released last year.

It’s a fusion of tribute act and 3D concert movie that transcends that description. At times it was possible to forget this wasn’t a live performance, though when the backing singers stepped forward to belt out “Does Your Mother Know,” a surge of live-music energy shot through the arena.

The four band members — two married couples during ABBA’s heyday, though now long divorced — got a rapturous ovation when they took a bow at the end of Thursday’s show, 50 years after they formed ABBA, and 40 years after they stopped performing live.

Watching one’s younger self perform must be a strange sensation, but the band members, now in their 70s, said they were delighted by the show.

“I never knew I had such amazing moves,” Ulvaeus said.

Lyngstad agreed: “I thought I was quite good, but I’m even better.”

Ulvaeus said the audience reaction was the most gratifying part of the experience.

“There’s an emotional connection between the avatars and the audience,” he said. “That’s the fantastic thing.”

Producers bill the show as “revolutionary.” Time will tell. Like the first audiences to watch a talking motion picture a century ago, attendees may leave wondering whether they are watching a gimmick, or the future.

The Times of London reviewer Will Hodgkinson judged the show “essentially an ABBA singalong with added sound and light show,” though he called the effect “captivating.” Writing in The Guardian, Alexis Petridis called the concert “jaw-dropping” and said “it’s so successful that it’s hard not to imagine other artists following suit.”

Gimmick or genius, “ABBA Voyage” is booking in London until May 2023, with a world tour planned after that.

The fans who attended Thursday’s show are just delighted ABBA is back.

“I’m so excited,” said Kristina Hagman, a Swede who has been a fan since the 1970s.

“I was bullied so much because you were not allowed to like ABBA at that time, because it was so commercial,” she said. “But now we are taking revenge.”