Through five albums and ten years, Fall Out Boy have made a startling stylistic departure, honing their roles as witty pop-punk upstarts on 2003 debut Take This to Your Grave, all the way into slick radio-pop provocateurs on this year’s unlikely comeback smash Save Rock and Roll. But to call it unexpected would only fit the defiant narrative the Chicago basement hardcore vets have spent the past decade defining.

A crossover from message boards to MTV with second album From Under the Cork Tree in spring 2003 was unexpected and felt immediate; a Jay-Z appearance kicked off their following album Infinity on High two years later as the first of many unexpected collaborations (a list that would, in time, go on to include Elvis Costello, Courtney Love, and Lil Wayne, among many others). Babyface also made an appearance on that album, but it was Butch Walker’s presence that most definitively helped shape the band’s trajectory. Having experienced the rise and fall of instant stardom with his own pop-rock group Marvelous 3 before transitioning to a career as a powerful pop producer and songwriter, Walker solidified Fall Out Boy’s transition from Chicago grit to California polish. Credited with production on only one song, “Don’t You Know Who I Think I Am?” Walker would foster bigger risks and relationships for the band. He would introduce them to Ryan Adams, leading eventually to their latest surprise—their second release in six months—Pax Am Days.

At just thirteen minutes, the eight-song, west-coast-hardcore-influenced EP is far from a game changer, something early reviews have been quick to indicate. But as with every Fall Out Boy release, it’s a necessary part of their chronicle. When word first got out that the band had spent time recording punk songs with notorious metalhead Adams, first thoughts assumed a return to the grit of Take This to Your Grave. That didn’t happen. In true Fall Out Boy fashion, the band opted to release an album that didn’t just pre-date their debut, but one that went back a decade or two further.

“I think that, growing up, we grew up fans of people like Bob Dylan doing whatever he wanted,” says bassist and lyricist Pete Wentz over the phone from home in L.A. only a day before heading to Indonesia for the band’s current Save Rock and Roll tour. “If he felt like he wanted to go up state and record with The Band, he’d go and do that. Or Metallica covering punk rock songs. You grow up with people that you look up to doing that, and I think that kind of spontaneity is lacking in today’s pop music.

“At some point, we just wanted to do something that was just for fun,” Wentz continues. “That’s the only reason we did it. There’s no real intention behind it as far as impressing anyone or getting it on the radio or anything like that.”

Pax Am Days could be seen as “an alternate reality of what Fall Out Boy could have been,” says Wentz, joking that it’s “noise for the sake of noise” before distinguishing its California sound from the band’s roots in Chicago hardcore. But it isn’t so much about quality as it is timing, and it works as a fitting denouement to the climactic Save Rock and Roll.

When Fall Out Boy fizzled out after 2008’s coolly received Folie à Deux, some assumed that was the end. Wentz sputtered with the electronically inspired Black Cards; singer/guitarist Patrick Stump expanded on his other influences with the aptly titled solo album Soul Punk to some success, while struggling publicly with overcoming Fall Out Boy’s legacy; drummer Andy Hurley had perhaps the biggest wave to ride post-Fall Out Boy, jumping headfirst back into the familiarity of the hardcore scene with crossover crust punks Enabler. Fall Out Boy never officially broke up; they called it a hiatus, and that was what they stuck with. But as time passed, Wentz, who at the time of the break stated that the world “needed a little less Pete Wentz,” felt less sure of the band’s future.

“You see your words get taken out of context a little bit, or your friends’ words, and you’re like, I don’t know? Are we broken up? Are we not broken up? A hiatus is definitely the weirdest, goofiest thing ever. It’s strange, but for us it was necessary. We needed to take that break.”

Then, Save Rock and Roll appeared and erased any doubts. Rumours about a return never really stopped the whole time the band was away, though they consistently, even up until the week before their surprise return announcement, denied it. When it was released in April, the band’s fifth album debuted at number one on Billboard’s Top 200, selling more than 150,000 copies in its first week, and, more than ever in the band’s career, largely won over critics, who called it everything from a “major accomplishment” to a “rather stunning renaissance.” Save Rock and Roll stamped a seal of approval on the band’s ambitious comeback, and Pax Am Days comes off as a thirteen-minute sigh of relief.

“I think Take This To Your Grave was really reactionary, like, ‘you did this to me,’ but this person’s probably not even listening,” explains Wentz. “Save Rock and Roll is aggressive, but it’s hopeful. It’s more thought out.”

Every Fall Out Boy album exists in the same universe. They’re about looking forward in the same world, about progressing. Pax Am Days is separate. Its turn toward primitive punk isn’t about recapturing the old spirit of Evening Out with Your Girlfriend, Take This To Your Grave, or even From Under the Cork Tree, but about playing outside of their established canon and comfort zone.

“It was fun to do something that was from a different time. Take This To Your Grave? We’ll leave that to somebody else to re-do,” says Wentz.” I think that sometimes it’s best to let the past rest in the past. If we were the band that wrote Take This To Your Grave over and over people would say ‘why doesn’t this band ever change, they suck.”

Instead fans can look to outside influences. Fall Out Boy consider themselves progressive, but not in the Moving Pictures-meets-Rick Wakeman tradition. That their career has straddled so many lines and been so hard to predict fits perfectly with the songs they’re trying to write—ones that push the boundaries within the confines of pop music and rock and roll. Save Rock and Roll isn’t a title to take literally, but a commentary on the stagnating scene. “At some point it’s interesting when rappers are the big rock stars,” says Wentz, and it’s that kind of thought that’s fostered their relationship with hip-hop.

“When we were talking about having a rapper [involved with the new album] originally, even before 2 Chainz [appeared in the video], everyone was like ‘you’re going to do that in the first video for a song off Save Rock and Roll? That seems like the least rock and roll thing to do,’” he says before simply summing up their approach not only to the album, but maybe their entire career. “And then it was like, wow, that’s definitely the most rock and roll thing to do if it’s the least rock and roll thing to do.

“How cool is rock and roll if the only possible outcome of it are guitars sold to dads at Guitar Center?” jokes Wentz. “When rock and roll was big, it was painted on the side of 747s, it was dangerous, it was interesting, and it was progressive. Just when you were sure about KISS, they took the make-up off.”

Save Rock and Roll—which itself features a Big Sean guest verse on “The Mighty Fall”—is far from Lick It Up, and for fans that’s a good thing. Fall Out Boy have always been less concerned about their image than their music, and while Wentz reveals Hans Zimmer as his dream collaboration, it’s his admiration for another Chicagoan that best defines his thoughts on progress—Kanye West.

“Whenever you get into his thing, he moves on to the next thing. He’s like, ‘now I do this thing,’ and you’re like ‘what do you mean? I finally understood this for the first time,’” says Wentz.

“I think that’s part of being a progressive artist. You’ve got to keep trying to push the boundaries a little bit.”