God only knows what was going through Black Thought’s mind during Spring Fling. On stage, the Roots’ MC seemed happy to rock the crowd with hits from the ’90s, covers of “SexyBack” and “Push It” and the antics of some guy with a sousaphone named Tuba Gooding Junior. But on the same day that Black entertained a bunch of drunken, mostly white kids, he and his band dropped “Rising Down,” a dark album centering on the MC’s failing attempts to make sense of his world. One wonders if Black was only half with us on Tuesday.

The Roots are generally known as “that one rap group I like, the one that, like, plays real instruments and stuff.” Whatever Black’s skills as an MC, he’s famous because he raps with a live band. And whatever the Roots’ merit as a band, their albums have been adored by critics because of the way they blend hip-hop with genres more comfortable to the average ear.

But “Rising Down” is different. This is Black’s album. Drummer ?uestlove (pronounced Questlove) lays down simple beat patterns and stays with them, withholding any improvisation. There are no chord changes in the bass lines. The keyboard parts could be played with one finger. These are not the lush cuts of previous Roots albums ­— these are minimalist hip-hop loops, full of empty space for Black to move in and out of.

Black fills this emptiness with rushed meditations on just about every problem on his mind right now. His verses are dense with thought, almost to the point of incomprehensibility — every word in his flow has a function, and he does not waste a single bar’s worth of time. Black is virtuosic in his ability to commune with a beat, to use its mood and rhythms to help express whatever his words can’t, and, at least for the first part of “Rising Down,” he pushes every one of ?uestlove’s tracks to near breaking point. But he can never get in all of what he wants to say, so he rushes right into the next song to try again. And again. And again.

Black’s intensity must have been contagious in the studio — almost all the guest MCs put in serious work. The album’s best track, “Get Busy,” is good because of how each rapper on it takes ?uestlove’s spartan beat and uses it as a launch pad for his own brand of verbal fireworks. Black comes in first, throwing down yet another stream of prophecy and anger about something like rebellion in Philadelphia. He overwhelms with words and rhymes, adding only slight variations to an otherwise constant stream of sixteenth notes. Dice Raw follows, employing simpler phrasing and rhythms but ending with what has to be the best image in the album: “Built like a tank, smoking on yay / Walking through the Guggenheim raw like black ink.” Then Peedi Crakk comes out of nowhere, spitting hard about how much he hates the Internet. WTF? Crakk’s flow is the antithesis of both Black’s and Dice’s: self-absorbed, curt and tense, always threatening to hop to a completely unrelated idea. Beginning with the same thing, each rapper molds it into a medium for his personality.

The track is great, but not enough for Black. In those that follow, he rearranges the guest roster, drawing from a pool of Roots regulars that include Dice, Malik B, Mos Def, and Talib Kweli. He switches up his subject matter, touching on inner-city violence, taxes, global warming, crappy pop songs, loss of passion for his work and a hundred other issues, both personal and private. Later in the album he ditches ?uestlove’s original bare beats and leads the band through nu-metal tracks, soul tracks, even tracks that (oh God why?) sound like lost Nickelback cuts. He’s groping for some kind of perfect combination, something that will encapsulate his angst. He never finds it: The album ends with a recording, or a reenactment, of an inconclusive argument between the Roots’ manager and a record exec, which ends finally with a car crash.

In an interview, ?uestlove called “Rising Down” the Roots’ “most incendiary, political album” of their career to date. But instead of getting an “incendiary, political” message, the listener just gets a self-portrait of Black as a man desperately grabbing at every problem in the world, trying to put it all into some kind of order, trying to make some kind of final judgment. The dude and his friends rap their asses off for a good hour, but in the end the listener gets the sense that, for Black to finally feel satisfied, “Rising Down” would have had to be never-ending, an infinite series of bare rhythms for him to rap over until he died.