Billboard — Six albums into a career that has mobilized and polarized the indie rap underground, the Minneapolis rapper Slug, one-half of acclaimed Rhymesayers duo Atmosphere, is finally stepping outside himself.

Something of a superstar in that indie-hip-hop galaxy and possibly the least likely teen-girl idol currently producing popular music, the 33-year-old Slug (Sean Daley, to his parents) has spent years airing out his journal entries on wax, rhyming at length about what sounded like a couple hundred therapy sessions’ worth of lady-friend problems and harvesting a large female fan base in the process.

But Atmosphere’s sixth and most accomplished record, “You Can’t Imagine How Much Fun We’re Having,” includes a few choice couplets that seem designed to make some longtime fans do a double-take and punch the back button on the iPod. Like this one: “I’m returning this bleeding hearts club membership card,” Slug raps in “Say Hey There,” “because I want no motherf***ing part of it.”

It’s not that Slug has reached some sort of sun-splashed plane with the ol’ personal life — “she’s drama, I’m drama, we’re drama” the newly mohawked rapper admits from a Detroit tour stop, with the sighing-but-not-unpleased resignation of someone who’s cool operating under that definition for the time being. It’s just that everything isn’t necessarily filtered through the holes in a broken heart anymore.

“And I don’t know why that is,” Slug admits. “In the past, I wrote so much about myself because I didn’t want to project. I wanted it to be: If you’re gonna hate the story, then hate me. But I’m learning it’s OK to project as long as I’m offering at least a closure, or an opportunity for [listeners] to dialogue with friends. With where my life has gone, I’m able to tell these stories without putting them through the relationship factory. And I’m happy about that.”

In a speed-talking interview that manages to reference Billy Joel and folk songwriter Shawn Phillips, Slug is, as his hip-hop persona would indicate, wide-open and stream-of-consciousness chatty. But he’s writing now with the grounding of someone who’s got some miles behind him, and nuggets of aged-sounding wisdom and self-awareness creep into his monologues.

“It never was about ‘Look at me and my self-centered world,’” he said, “But I found a path of writing where I was able to personify any problem I saw as a relationship problem. So what happened was I was making all these songs about dysfunctional co-dependent relationships, when the song was about George W., or how I feel about the gentrification of [Chicago's] Wicker Park, for Chrissakes.”

Slug attributes that externalizing to two factors: the severe reduction of his “self-medicating in general” and his adoption of a slightly more distanced role in his writing. “I’ve always been sitting in the watchtower observing,” he said, “But now I’ve totally climbed into the observer mode, as ‘This is my job.’ I watch people, and form ideas and bulls*** opinions about people, but I never wanted to come off as that guy on the soapbox preaching to the choir, because for so long, the kids that come to my shows are the choir.”

Between Slug’s lyrical stretches and Ant’s melodic, big-beat production, “You Can’t Imagine” represents Atmosphere’s best shot at breaking out of that underground to date. Not that it’s anywhere within shooting distance of mainstream — tracks like “Little Man,” a generation-jumping look at father-son relationships, are still more likely to pop up on NPR or a blog than radio. But “Watch Out” bangs like old LL Cool J (who gets a glancing lyrical half-shout) and “Get Fly” cribs a joyous gospel sample to underwrite its cautiously sunny worldview: “I can’t fight your war until I’m finished with mine.”

“I do think this is probably our darkest release, but, you know, it goes hand in hand with these being probably the darkest two years of my life,” Slug said. “I’d have to say that Ant, even probably more, had duress on his shoulders over the last two years than normal as well.”

But, he added, they never set out to make a dark-soul-of-the-night kind of record, or anything more than their usual “concept” of “following this guy Sean around.”

“[Ant and I] get together on Sunday and Saturday and have a great time making new songs about having a bad time,” he said. “It’s a really odd situation. And we sit around and laugh and try to make each other react to what we’re doing and when we’re finished we look at it and go, ‘It was a lot more fun to make that record than it is to listen to it.’”

“Panic Attack” bears that out — it’s a shuffling, fuzzy beat about America’s desperate overrealiance on medication. “Say Hey There” has a sing-song-y hook and verses in which Slug tries to step out of the image he’s created for himself. But the album’s best evidence of that is “That Night,” which opens sounding like a club banger and turns into a thanklessly tragic tale about the 2003 murder of a teenage fan after an Atmosphere concert in Albuquerque, N.M.

“When [Ant] sent me that beat, I said, ‘What do you want me to rap about? This is a dance song. I can’t come in here and be all aggressive.’ And he literally told me go and write a song that you’re not supposed to write, and that was the one song I’ve been afraid to write for two years now. I didn’t know I’d be able to write a journal about it, much less a song.”

It came together quick. “I went home that night, wrote it, took it back and said, ‘Here’s what I got.’ It’s the first time in my life that a song was only alive for under 24 hours and still made the record.”

Still, Slug, true to his hip-hop persona, is quick to launch praise for helping structure the record, from its old-school-tinted beats to its unmistakable sense of trying to find a balance.

“His deal was to be careful to always make sure to throw some lightness on, especially on some of the darkest songs,” Slug said. “Instead of being on some like ‘The world’s gonna end and we’re all gonna die’ s***, he’ll bring a pop sensibility to the music. That he thinks like this is amazing to me. To me it’s like, ‘There’s the beat, dog. Rap.’”

But Slug’s also got the unmistakably shifting priorities of a guy who’s getting older. “My son’s 11,” he says, “and last night in Chicago, there were kids that couldn’t have been old enough to have a learners’ permit. And now I think I’m growing in my position and I want to do the right thing with it. Maybe in a room full of 1,000 kids, I might just be able to divert two of them from becoming future frat-boy date rapists. And I think that’s why a lot of my writing has naturally refined itself. That’s kind of where I wanted to be all along — I just never knew it.”