In the seven years since Silent Shout, the Knife's mythology has grown to the point where the Swedish duo seem like something other than a band. "Band” implies people banging on things widely agreed upon as instruments and making things that most people would recognize as "music"-- this feels like an inadequately pedestrian way to describe what Karin Dreijer Andersson and Olof Dreijer are. Perhaps even more so in their absence, the Knife have come to seem like a vibe, an ethic, a dark, not-entirely-scientifically-understood phenomena; other bands are to the Knife what matter is to anti-matter. When new artists say they’ve been influenced by the Knife-- and it’s a claim countless have made in the past few years-- they are at this point referencing not just a specific sound but an entire way of being in our information-glutted world: a desire to retain a tightly controlled, precisely evocative sense of mystery and mastery over their image. Even in the wake of such pollutants as international success, ubiquitous acclaim, and frequent imitation, the Knife have found a way to keep their name meaning something remarkably unique and pure.

This has something to do with the fact that Andersson and Dreijer have gone to great lengths to come off like they are something other than human. On stage, they were silhouettes glowing behind a translucent screen. They gave interviews and accepted awards in disguise (moving through a terrifying cycle of bird masks, Dystopian Blue Man Group masks, primate-inspired facepaint, and of course who could forget Andersson's infamous melting flesh mask?). And on the steely, electro-nightmare Silent Shout-- their first great record-- they found new ways to viscerally integrate these ideas into their sound, warping and pitch-shifting Andersson’s vocals until they grew androgynous and post-human. Somewhere in the past seven years, the Knife reached that Lynchian status where everything they do is their own, adjectivally specific kind of creepy. The early press photos for their new album, Shaking the Habitual, made an activity as innocent as swinging on playground swings feel forebodingly sinister.

But buying "post-human" mythology wholesale has always sold the Knife a little short. After all, what was their breakthrough hit "Heartbeats" if not a heavy-breathing declaration of vulnerability? Even Silent Shout cut through the abstraction and found a pulse-- whether it was the strobe-lit dancefloor rhythms of “We Share Our Mothers’ Health” and “Neverland” or the palpitating storytelling of a song like “Forest Families”. The driving force of their music is the interplay between the uncanny and the familiar, though in all the theatricality it's easy to forget the latter. But the early information that trickled out about Shaking the Habitual served as a reminder. We’re so used to experiencing the Knife at a cool, veiled distance that the most shocking things about their return were the ones that seemed uncharacteristically personable: their faces (on full display in the anarchic video for “Full of Fire”), their fingernails, their smiles (were they actually smiling in that photo?). For all their sinister, shadowy abstraction, the Knife are at their most disarming and affecting when you’re briefly reminded-- and you often are, over the course of their sprawling, magnificent fourth album Shaking the Habitual-- that Andersson and Dreijer are human after all.

Boundary-busting in content and in form, the 2xCD Shaking the Habitual challenges plenty of perceived notions-- about extreme wealth, the patriarchy, the monarchy, environmental degradation, decreasing attention spans (“It's nice to play with people's time these days,” Andersson says in explanation of the record's marathon length), and not the least of which the Knife's own identity as a band. The winding, unbridled song structures and industrial-tinged, organic sounds are such a departure from the rest of their output that they’ve said they initially considered releasing it under a different name. Shaking certainly pulls from a wider aesthetic palette than any of their previous records: found sound drones (they crafted the 19-minute “Old Dreams Waiting to Be Realized” from editing hours of electronic feedback they'd recorded in a boiler room), zithers, an instrument they apparently made out of “an old bedspring” and “a microphone”-- all employed in the name of breaking their own habits. “We went temporarily acoustic,” they declared in the madcap manifesto that served as Shaking's press bio. “Electronic is just one place in the body.”

In plenty of ways, Shaking seems to have “inaccessible” etched into every fiber of its DNA. It is 98 minutes long (about double the length of the already-epic-seeming Silent Shout). Six of its thirteen songs exceed eight minutes. The official statements released with its music videos (“'A Tooth For An Eye' deconstructs images of maleness, power and leadership. Who are the people we trust as our leaders and why? What do we have to learn from those we consider inferior?”) read like museum placards. There are two long, dissonant drone pieces-- and one of them has the feel-good title “Fracking Fluid Injection”. But once you surrender to these facts and descend into Shaking the Habitual, its atmosphere is strangely, surprisingly inhabitable. Moving fluidly between potent bursts of electro-aggression (“A Tooth for an Eye”), seductively uncoiling, meditative grooves (“Raging Lung”) and ambient stretches, Shaking the Habitual-- like Swans’ recent and similarly mammoth The Seer-- doesn’t demand the same kind of attention the whole time. Many of the things that might seem off-putting in theory are what make it hang together so well as a front-to-back listen-- the drone pieces are sequenced such that they act as intermissions, though the kind where the air conditioner's at an uncomfortable full blast and the house lights remain, evocatively, dark. Put it on in a room and it snakes in and out of your consciousness, but on some level it’ll still have you in its chilling, atmospheric vice grip.

Following Andersson and Dreijer down such a labyrinthine rabbit hole would be difficult if they didn’t hook you from the start, but luckily the first three songs are among the most immediately arresting 25 minutes of music the Knife has ever made. “A Tooth for an Eye” almost feels like a belated, revisionist do-over of the band’s relatively unremarkable early work. While 2003's Deep Cuts sometimes struggled to find common ground between punk aggression and bright, calypso-tinged synths, “Tooth” ties these competing impulses together seamlessly as it also deftly weaves in a political message. The song’s refrain comes from the experimental British writer Jeanette Winterson’s book The Passion (the interstitials "Oryx" and "Crake" also reference a Margaret Atwood novel), but Andersson brings a physicality to her delivery that muscles the line right off the page: “I’m telling you stories,” she seethes, until you can almost see the vein bulging in her neck, “Trust meeeee.”

The polyrhythmic, polymorphously perverse industrial throb “Full of Fire” feeds off the heat kindled by the opening track and rides it for a magnificently maniacal nine minutes, while the creaking, evocative “A Cherry on Top” has got to be one most deliciously creepy Knife songs yet-- of course, that’s saying a lot. (At times it sounds like Animal Collective's “The Bees”, but makes that haunting track sound like a lullaby in comparison.) Built around the bone-curdling sound of a zither warping in and out of tune, Andersson sings of riches-- “Strawberry, melon, cherry on top…The Haga Castle evening cream”-- in a heavy, manipulated voice so overripe it basically wafts decay. She's clearly having fun inhabiting the role of the fat-with-power monarch here, but her roleplaying is also an act of resistance (the band has recently cited as an influence the gender theorist Judith Butler, who pioneered the notion of thinking about gender as performance), of cutting the omnipotent down to size and suggesting that the institution's expiration date has passed. As the instrument warbles in and out of tune, the castle walls-- and the confines of pop structure as we know it-- seem to be crumbling at her and Dreijer's feet.

Nothing else quite matches this opening run, but the second disc has its highlights: The frenetic, gargling instrumental “Networking” recalls the best of Dreijer's techno work as Oni Ayhun and proves he can still scramble the conventions of electronic music with an effortlessness that puts him miles ahead of the Knife's many imitators. Then there's “Raging Lung”, a dank, serpentine 10-minute groove that lifts its refrain ("what a difference a little difference would make") from Fugazi's classic 1990 debut Repeater. Tipping its hat to the ideologies of punk rock, gender outlaws, enviro-anarchists, and outsiders of any stripe, Shaking feels at time like a guided, international tour through the last quarter century of political resistance and radical thought-- or maybe an epic, authority-fucking mural painted in the part of town where all the squatters and crust punks have migrated. The most difficult part of making a record so ambitious and conceptual is, of course, bridging the gap between thinking and feeling-- a divide that even Shaking cannot always conquer. But all things considered, it's remarkable how seldom the Knife actually sound like they're guiding these songs with their brains rather than their hips or fists. Even at its most cerebreal, this record is palpably, poundingly alive.

Though not as challenging as their collaborative opera score Tomorrow in a Year, Shaking still knowingly, brazenly risks turning less adventurous listeners off-- and maybe those who dismiss the record for not trying to recreate the populist magic of "Heartbeats" or "We Share Our Mother's Health" have a point. The Knife would clearly like to use their music to incite the listener to rethink concepts taken for granted and challenge authority, but would a more effective method of shaking the habitual be, say, smuggling a subversive message into the greatest (and at press time, only) four-minute dancefloor anthem ever written about fracking? Regardless of the answer, that's a question the Knife are no longer interested in exploring. "The most commercial way would have been to stick with a formula," Andersson observed in a recent Pitchfork interview, but then dismissed that option entirely, saying she and her brother had now moved on to questioning conventions "on a structural level rather than a psychological level." And in the end, though, Shaking's unruly structure-- a perfect union of form and content-- feels like a noble choice. In interviews, they've spoken about "the importance of making your privileges transparent in order to say something political." And the great privilege of being the Knife in 2013 is having a platform-- they've earned a devoted audience ready to approach their wildest, most challenging and passionate vision with eager ears and an open mind.

Shaking the Habitual is, inarguably, an achievement. It is the Knife's most political, ambitious, accomplished album, but in a strange way it also feels like its most personal: It provides a glimpse into the desires, intellectual enthusiasms and (unsurprisingly dense) reading list guiding one of music's most shadowy duos. At its most mesmerizing, its conceptual rigor and occasional inscrutability are overpowered by a disarming earnestness: It is a musical manifesto advocating for a better, fairer, weirder world. Shaking the Habitual feels not post-human but profoundly humanist, fueled by an unfashionable but profoundly refreshing faith in music's ability to hypnotize, to agitate, and to liberate-- to become, in Winterson's words, "the high note that smashes the glass and spills the liquid."