In some ways, Arctic Monkeys looked as vintage as they could: the letters “MONKEYS” appeared behind the stage in old-timey off-white, and the gargantuan main-stage screens showed the band in grayscale (a somewhat pretentious but admittedly cool look). In others, they looked unmistakably contemporary: Frontman Alex Turner sweated valiantly under a very hip button-up, at least until yielding and stripping to his undershirt, and wore clear sunglasses on his shaved head. Much like their most recent album, “Tranquility Base Hotel and Casino,” it either represented a brilliant synthesis of retro and modern or an identity crisis for Britain’s biggest band.

That album, which divided both critics and fans, showed the growing art-rock ambitions of the former garage-indie quartet. Likewise, their Lolla set was more Pink Floyd than The Strokes from the very beginning: They entered to ominously flashing red lights and began with a track from “Tranquility Base,” “Four Out of Five.” Throughout, their 2013 songs from “AM” and “Tranquility Base” worked better than their older material—partly because the massive festival speakers could better handle their simpler and more spaced-out sounds, partly because the tired end-of-day crowd was largely more ready to groove than to rock out, but mostly because “Star Treatment” better fits the band’s current look and presence than “I Bet You Look Good on the Dancefloor.” And Arctic Monkeys simply seem more interested in playing their space-rock than post-punk.

Still, they interspersed old favorites (and some surprising minor tracks) from “Humbug” and “Favourite Worst Nightmare,” though notably not mega-hit “Fluorescent Adolescent,” with the songs from their last two albums. Wisely, they saved the most popular “AM” tracks—the question-mark trio of “Why’d You Only Call Me When You’re High?,” “Do I Wanna Know?,” and “R U Mine?”—for the show’s second half. In a somewhat unusual move for Lolla acts, they included an extended encore, running 20 minutes over their allotted 75-minute headliner slot. Fans who remained were rewarded with “Star Treatment,” “Snap Out of It,” and “R U Mine?,” hits (from the last two albums) whose familiarity made them an ideal end of the night.

Arctic Monkeys’ future experiments, whether with Dr. Dre-inspired beats or space-themed concept albums or something else entirely, will likely evince a continuing battle between the old and new. We’ll see whether their next era will take rock into the 2020s and save the album itself or send them backsliding into nostalgia. But at Lolla, the old was the new: The ’70s-esque, album-oriented lounge pop of “Tranquility Base,” even in black and white, seemed to point the way forward (at least for the band) more than their 2000s modern rock or even the hip-hop of “AM.”

—Staff writer Trevor J. Levin can be reached at trevor.levin@thecrimson.com.