Lunch in Athens is taken at a restaurant with a rosette in its window proclaiming “Best Fried Dessert”, next door to a general store that prominently displays canoes, axes and windchimes. En route, Howard gesticulates with a cigarette in one hand, toggles through songs on her iPhone with the other, and mostly leaves the driving to her truck’s own intuition. “Oh my God, I ain’t no singer ‘til I can sing this,” she announces, as Aaron Neville’s version of “Ave Maria”, starts up. She listens in silence, reverently, for a couple of minutes. “Gives. No. Fucks,” she eventually decides, then moves on to another of her favourite songs, “Basketball Jones” by Cheech & Chong.

We drive past a dilapidated shack on the outskirts of Athens, sheets of rusted, corrugated iron balanced improbably on it for a roof. “There’s people actually live there,” says Howard, pointedly non-judgmental. “They don’t have any power and they heat up water on a wood stove. And you can’t offer them any money ‘cos they don’t want it, they just want to live that way. They’re a really old couple in their seventies who collect government cheques and spend them on liquor. That’s their life.”

Howard, 26, once investigated her genealogy and discovered that her family, on both sides, had been in Athens since before Alabama was even a state; when it was called, she says, “unclaimed territory”. Her old schoolfriend Zac Cockrell, the bassist in the Alabama Shakes, lives on land where his great-grandfather once ran a junkyard. Nearby is the barn in which his grandmother was born, long graffitied with satanic symbols.

Since Boys & Girls became an international phenomenon in 2012, the Shakes have been cherished and championed by music fans with a historical and sometimes romantic belief in the idea of Southern Soul, as if a certain groove and drama was inherent in the local populace. Muscle Shoals, a quick glance at the map reveals, is only an hour’s drive away. The Alabama Shakes’ understanding of musical lore and tradition turns out, though, to be a little more acquired than instinctual. Their tastes extend to an enduring appreciation of the first My Chemical Romance album, and the fact that their often powerful and resonant music can invoke Southern archetypes like Otis Redding – as it does on, say, “You Ain’t Alone” on Boys & Girls, and “Miss You” on Sound & Color – is, they insist, nothing to do with geographical location.

“Athens is a working town, and it was just by miracle that we got together,” says Brittany Howard. “I didn’t know until I was 19 years old that anything happened in Muscle Shoals, they don’t teach us that. I was always like, ‘This is a really great Clarence Carter song’ – I had no idea where it was made.”

If they evade easy definitions of a Southern band, however, the Shakes have a loyalty and connection to their hometown which goes far beyond music. Driving around with them can become a kind of Alabama picaresque, where haunted houses and abandoned country clubs seem to lurk round every bend in the road, where each vista is judged by how it looked before and after the last major tornado blew through Athens and East Limestone County.

“My Ma used to tell us this story that a tornado jumps a railroad track,” Howard says. “I guess she told it to us so we didn’t get scared.” Four years ago, the Shakes were meant to be driving to New Orleans for a gig with Hurray For The Riff Raff, when a major tornado gave them “the slightest glimpse” of what, as Howard describes it, “an apocalypse might be like.”

A postal delivery worker at the time, Howard rose at five the next morning, drove ten miles to Elkmont for petrol, then went back to bed. Cockrell remembers waking up with no power. “I was,” he recalls, with what proves to be typical drollness, “cooking hot dogs over a candle.”

Howard, Cockrell, guitarist Heath Fogg and drummer Steve Johnson are the sort of four disparate characters who would never have ended up in a band together if they’d lived in a big city. Blake Mills describes them as “a group of highly individualised individuals.” “They’re not a clique,” he says, “they’re not a band who all wear costumes and look alike. They’re a strange group of people. Heath’s this clean-cut, straight-shooting, earnest guy, and Zac is this sort of loveable mascot. Nobody can make me laugh whenever they want to as much or as easily as Zac. If they hadn’t plucked Steve out of the music shop he was working in, he may well have found himself on a varsity football squad. His background is not in funk or R&B. His background is Alice In Chains and Soundgarden.

“And Brittany is this powerhouse, she’s this presence. To be in a room with her is to feel some sort of electromagnetic field that emanates from her.

Courteous and for the most part reserved, The Alabama Shakes do not generally appear to be an over-analytical band. Mills, for all his empathy in the studio, has a different perspective, and can examine them more objectively. “I have my own theories about how unhealthy democracy is when it comes to bands,” he continues, a solo artist in his own right. “There’s a desire for democracy in this band, and yet there’s also the reality of what each person brings to it. Everybody’s not trying to bring the same dish to the potluck, if you know what I mean.

“Zac and Steve and Heath, they look to Brittany for certain cues to react and emote to, to respond to. They’re all fully aware of what Brittany can do when she has a microphone, and I think they all celebrate it in the way that they play. It feels like a natural dynamic; it doesn’t feel hierarchical, but there’s a workflow. They have this organic kind of nonchalance, and for me that’s the most Southern thing about them. They’re a very soulful, heartfelt, unpremeditated group of musicians.”

Brittany Howard is defiant and, perhaps, a touch anxious about the reception that awaits her new album, a radical expansion of the Shakes’ modus operandi after the unadorned garage-soul of Boys & Girls. There are, for sure, relatively unadorned garage-soul songs on Sound & Color – “The Greatest” is even a punkish ramalam that Blake Mills compares with The Ramones, and with live Otis Redding performances – but they co-exist with a more warped, abstracted music that taps into a futurist strain of R&B running from Funkadelic, through Prince, to Erykah Badu. The sense of a band on a profound historical timeline remains, but it will be harder for the Shakes’ critics to diminish them as a good-time retro act this time out. “I’m not sure what people will be expecting, but they won’t be expecting this,” says Howard.

Brass, for example, has remained off the agenda, in spite of its potential affinity with the band’s sound. Where a blaring horn section could have stepped in on “Future People”, a distorted Farfisa arrives instead. “It puts the song in a completely different and more ambiguous genre,” says Heath Fogg. “We all like that more than pigeonholing ourselves with the classic R&B thing that started building up around the last record.”

“You don’t get to be your creative self when you’re just following a tradition,” adds Howard. “The education I got in music was boundless, that’s how I know music. Music is everything that ever is, ever was, and you can take from that what you will. It’s like language. People say, ‘There’s no original anymore,’ and I say, ‘OK, but there’s me.’”

An undercurrent of stress, or at least frustration, also seems to be present through much of Sound & Color, most notably on the lovely “Guess Who” – the album’s most overt Curtis homage – when Howard sings, “All I really want is peace of mind.” It’s easy to assume that the pressure stems from trying to top such a garlanded and lucrative debut album. Howard, though, is adamant that’s not the case.

“It’s just natural stress,” she says. “I have a very busy mind anyway. I’m not a worrier, I’m a thinker, and I can sometimes work myself into a frizzle-frazzle, where things coming out of my mouth don’t even make sense.”

“I was told before starting the record that she’s very hard on herself when it comes to singing, and difficult to satisfy,” says Blake Mills. “I think the real problem before was her not having a clear goal. Once she had that, she could sing in all these different ways, and it worked best when she would take a chance. She also has to deal with the clumsy way in which people make comparisons; stupid shit like the references to Janis Joplin. You throw most of that away and there’s still a stickiness that’s hard to get off your fingers, or off the bottom of your shoe.

“I think she’s aware of what she’s capable of. But I think the frustration comes from her desire to not just be somebody who displays what they’re capable of, but who actually has a discerning sense of what they want to achieve with that power. That’s where her fire and ferocity emanate from. The smalltown upbringing and sheltered lifestyle, I think, was too small a fishbowl for her brain. She’s a young adult, travelling the world and listening to new records, and all of that is culminating in her trying to make something new or futuristic, and something that feels soulful, but not like soul music. Her fearlessness is something I hope doesn’t run out.”