One guy sings and slings an ax, the other pounds away on a drum kit. Those are the bones of rock 'n' roll, the essence of the genre in its purest, rawest form.For the Black Keys, it's a little more complicated than that. A lot, actually.Behind Dan Auerbach and Patrick Carney's two-man garage rock revolution — one that has yielded massive airplay and endless critical hosannas — is a maze of musical complexity. The duo's Turn Blue world tour, which hits Tampa's Amalie Arena on Tuesday, is the biggest road show they've ever produced, with a sprawling stage swarmed by glowing, Transformer-like screens.Maybe all the bells and whistles are warranted — this is, after all, the duo's first local gig in four years, their first as headliners since 2005 at Skipper's Smokehouse (my, how times have changed). Or maybe they'll make you wonder what happened to the stripped-down sound that got the Keys here in the first place.Things change when you reach the A-list. No longer are the Black Keys just a scruffy singer and gangly drummer screaming and walloping like two teenagers in the basement. They're two of America's biggest rock stars, and with every album, they're acting more and more like it.But that doesn't mean it comes easy.Evolution of a revolutionStrangely, nothing about the Black Keys' first 10 years indicated they were on their way to this kind of superstardom. Critics and bloggers swooned for their distorted, punkish blues; tunes like Your Touch and I Got Mine popped up in films, commercials and TV shows. But as much as their music grabbed you and shook you, it never felt remotely like stadium rock.Brothers changed all that. Co-produced with Danger Mouse (Gnarls Barkley, Broken Bells), the 2010 album infused the group's signature romper-stomper sizzle with organs, whistles, handclaps, bass lines and reverb that recalled the spooky '60s and '70s soul of Creedence Clearwater Revival and Cream. The Keys added two members to their live act to play songs from Brothers (though Auerbach and Carney would still perform earlier songs as a duo).From there, it was off to the races. The cover of Rolling Stone, Saturday Night Live (twice in 2011 alone!) Grammy after Grammy after Grammy — Auerbach and Carney could do no wrong, and they followed Brothers with an album that swaggers like they knew it. El Camino (2011) was a celebratory blast of swinging hot-doggery whose centerpiece singles, Lonely Boy and Gold On the Ceiling, became the Keys' biggest crossover hits. That's when arenas came calling.This sort of thing just doesn't happen to bands on their sixth and seventh albums. It shouldn't be this easy. And it wasn't: It took three years — by far the band's longest stretch between projects — to release No. 8, this year's Turn Blue.It was during that break that things got complicated.At the top, a distorted viewDuring the break between El Camino and Turn Blue, the guys stretched their creative legs by producing albums for other artists — Auerbach worked with Dr. John, Lana Del Rey and Ray LaMontagne; Carney the indie pop band Tennis. They also found out that rock stardom comes hand in hand with, well, stardom. Auerbach and Carney always had a way with words, a good sense of humor and not much of a filter. And that's fine when you're a two-man club band way off the radar of most pop music fans. But when you're an A-lister, a lot more people start paying attention to what you have to say.When Carney tossed a mild diss Justin Bieber's way after the 2013 Grammys, Bieber tweeted: the black keys drummer should be slapped around, prompting a tsunami of Belieber rage aimed directly his way. (Carney later doubled down, calling Bieber "a (expletive) irresponsible a------.") Carney made headlines again by calling Nickelback "watered-down, post-grunge crap," and the reason "rock 'n' roll is dying." (This, the Canadian rockers laughed off.)And then there was the Keys' uncomfortably public feud with Jack White, a man who knows a thing or two about global success in a blues-rock duo. It began during the former White Stripe's divorce trial, when emails surfaced in which White accused Auerbach of trying to "follow me around and copy me and push himself into my world." Carney responded by calling White an "a------"; White then told Rolling Stone the Black Keys were like "a watered-down version of the original." The Keys-White beef seems to be temporarily squashed. (White released a statement reading, "Lord knows that I can tell you myself how hard it is to get people to pay attention to a two-piece band with a plastic guitar, so any attention that the Black Keys can get in this world I wish it for them.") The point is this: A decade ago, who could have predicted that a blues-rock duo from Akron, Ohio, would be making regular headlines on TMZ?A new 'Turn'Chalk it up to outside collaborations, discomfort in the spotlight or ennui with their workmanlike sound, but the band took a darker, more experimental left on Turn Blue, embracing moody psychedelia over dirty, distorted riffs. The album debuted at No. 1, and lead single Fever was a hit — proof that fans of serious guitar rock may be willing to follow the Keys' grimy, guttural muse wherever she may lead them. "Between El Camino and Turn Blue, we've seen rock get sucked out of the alternative music world," said Joel Weiss, music director for St. Petersburg alternative rock station 97X. "The bands that are on the pop side of alternative, it's all about bright, shiny, late-'80s production. That's the kind of stuff I can't stand. I'm a rock guy."Still, compare Turn Blue to the Keys' 2002 debut, The Big Come Up. It's a whole lot bigger, a whole lot crazier, and for every new fan the group gains, there might be one or two who are not quite cool with the change. Despite all the equity and critical goodwill the band has built up over the past decade-plus, their latest single, Gotta Get Away, stalled on the charts. "They've put out seven singles to alternative radio, and Gotta Get Away is the only one that did not go top 3," Weiss noted.This is how it goes at the top. Pressures increase. Expectations heighten. Hints of a backlash start to surface. "I'm seeing signs that maybe they're not getting the penetration that they once did," Weiss said. "I think if they get a lot weirder, they might have trouble."But there's an upshot, Weiss said. "I also don't think they're the kind of band that would give a crap. They're going to make the kind of music they want to make. … As long as it's Dan's guitar and voice and Patrick's drums, that's the core of the Black Keys."And they make it look so simple.