As Alex Turner sat at home in Los Angeles writing at the piano he’d received as a 30th birthday present, he wasn’t sure if the songs that were coming out of him were for Arctic Monkeys or a different sort of project. They certainly didn’t sound like anything the Sheffield quartet had just finished touring the world with. This was music that shook off the futuristic blend of rock riffing and R&B-ish grooves that underpinned 2013’s AM in favour of something altogether more retro and lounge-y. But upon hearing demo versions of the songs that Turner had fleshed out on an eight-track recorder, his bandmates convinced the frontman that this was where they should be heading next. Arctic Monkeys were about to embark on their most cosmic adventure yet. In the same way that AM established that the four-piece were no longer drawing inspiration from street-level shenanigans around Sheffield, Tranquility Base Hotel & Casino cast aside the notion of Arctic Monkeys as the next superstar purveyors of anthemic indie rock, mainly because there was zero sign of any anthemic indie rock on this sixth album. In its place was something more daring and ambitious. Not since Radiohead followed up OK Computer with Kid A had a Glastonbury headliner-level guitar band so deliciously wrong-footed their audience. Much in the same way that Thom Yorke’s band had transformed, Arctic Monkeys had found a new sound that was an effortlessly natural fit. Throughout the record, Turner excels in his role as the louche, wry piano-playing narrator at the centre of these songs, the music around him gliding from hazy funk to psychedelic soul, with the crackled groove of ’70s film soundtracks here and a ’70s classic rock sway there. Recording AM, the group had wanted to evolve beyond sounding like four people playing the same traditional instruments together and here they broke another rock band norm, enlisting a rabble of friends and musicians, including producer James Ford, Tame Impala bassist Cam Avery, and former Klaxons frontman James Righton, to contribute to recording sessions at La Frette, a residential studio on the outskirts of Paris. There was a spirit of collaboration at the heart of these songs, something that gives Tranquility Base Hotel & Casino its bewitching sense of constant movement. “Intermittently, you go between this idea that, ‘Oh, it still sounds like the band has got something else about it,’ and an uncertainty about how it’s going to be received,” Turner told Apple Music in 2022 about this evolution of sound. “But through the process of going between those two things, that idea is compounded. Where do we fit these songs into the show that is put together from all these other records from the past? How is that going to work? How [is] this thing that feels like it has a lounge-y jazz sample thing going to hang out with the rest of the things on the set list? But you find a way and, by the end of it, the songs all make their little adjustments and you find a through line.” They may have taken a risk but they got the rewards. The record went to No. 1 in the UK album charts and made the Top 10 in the US Billboard chart. A concept album telling the tale of a futuristic colony on the moon, like all the best sci-fi, Tranquility Base Hotel & Casino has escapism at its heart. It was the sound of Arctic Monkeys leaving themselves behind. A dramatic reinvention had paid off.