Nathaniel Rateliff is certain he has performed in Calgary before.But he thinks it was probably in a past life. Or at least a life before he formed his raucous backup band, The Night Sweats, and found stardom when he was just a few years shy of his 40th birthday. It’s been one of the more intriguing transformations and rock-star success stories of the past few years. One of its key planks is that there is a distinct before and after — pre-Night Sweat and post-Night Sweat periods — when it comes to Rateliff’s career.The before was dominated by a few acclaimed, if commercially unsuccessful, albums of broodingly dark singer-songwriter fare that have been compared to Leonard Cohen and Nick Drake. The after is dominated by songs powered by the seven-piece, soulful Night Sweats, who back Rateliff’s alternately honeyed and gruff vocals and tales about booze and love with a celebratory sound that unabashedly recalls early soul and R & B records. Their self-titled 2015 debut was even released on iconic soul label, Stax Records.“This was the type of music I always wanted to do,” says the Denver-based singer in an interview with Postmedia. “I had never figured out how to write it. It just came to me one day and I just ran with it.”The public breakthrough was S.O.B., a jubilant, gospel-fuelled stomper about alcohol dependency that rocketed Rateliff and his Night Sweats to international fame. Terms such as “improbable” and “surprise hit” are often used when describing the song’s meteoric rise and the immediate impact it had on Rateliff’s career. David Fricke, for instance, wrote in Rolling Stone that the Night Sweats “may be the most improbable breakout of this viral-pop-star decade: a white classic-soul band led by a burly middle-aged singer.”But it’s also the sort of song that could easily define a career, forever relegating the Night Sweats to the one-hit-wonder ghetto. So Rateliff and his band took a sensible approach when recording 2018’s Tearing at the Seams, the Night Sweat’s proper sophomore record after following up its debut with both an EP and live recording. Not only did they not try to top S.O.B. with a song in a similar vein, they didn’t really think about the charts at all.“Going into it, the people I work with — my management and people at the label — everybody was like: ‘You don’t need to make another song like S.O.B., just make a record you really care about.’ Even with the first record, some of the response to that was such a surprise. You can’t really plan for that stuff. We’re not trying to generate hits. We’re just trying to make records we like.”Still, Rateliff did take a different approach for the second record. The debut, which he recorded with the late Richard Swift, was more of a solitary affair, even if the end results seem to exude a benevolent gang-like camaraderie.“The first record was a lot of just me in the studio with Richard Swift and then (drummer) Patrick Meese joined us a week into that process,” Rateliff says. “The second record, after two years on the road doing 200-plus dates a year, we just really became a band. The second record was really focused on us playing together and what each person contributes to the sound and what we’re doing.”It may not have yielded anything as immediately earth-shattering as S.O.B. But the breezy mid-tempo You Worry Me, which sounds absolutely nothing like the band’s biggest hit, did climb the charts upon its 2018 release.Much of the album was recorded live-off-the-floor, which makes the material perfectly suited for the stage. As with the first record, there is a distinct retro feel to much of the material, from the stately horns that frame Be There, to the classic Motown shuffle of Baby I Lost My Way (But I’m Going Home) or soulful slow-grooved funk of opener Shoe Boot, which sounds like vintage Band.The Night Sweats will play the Calgary Folk Music Festival on Saturday, part of a final run of summer shows for Tearing at the Seams before the band returns to the studio.In fact, Rateliff is also recording material for a solo record, which will apparently recall his earlier singer-songwriter material. He has said in the past that finding success relatively late in life rather than 20 years ago has been healthy. He has certainly been open about his history and past demons, often talking to the press about his small-town evangelical upbringing (As an aside, he says he played music in church but not the cool Soul Stirrers and Staple Sisters stuff that inspired his later take on joyful gospel.) and even his own harrowing battles with alcoholism that he outlines so tunefully in S.O.B.“I still write about myself and the way I see things or situations I see,” he says. ” (S.O.B.) was autobiographical but I’m a long time removed from the particular incident so it doesn’t bother me too much. It’s been a fun song for us to see people get excited about.”Nathaniel Rateliff and the Night Sweats play main stage Saturday at 10:15 p.m. in Prince’s Island Park as part of the Calgary Folk Music Festival.