The new Sleigh Bells album begins with applause. The deafening roar of a stadium crowd builds as vocalist Alexis Krauss screams, “New Orleans! What the fuck’s up?” This mock-live opening track has all the hallmarks of the band’s wildly successful first album, “Treats”: the heavily distorted guitar, the explosive snare-drum hits, and Krauss’s cheerleader-shout vocals. It’s as if nothing has changed.

But “True Shred Guitar” is a false opening. Once the applause has subsided, Krauss and guitarist and producer Derek Miller are finished with congratulating themselves on a job well done on their debut. By the second track, “Born to Lose,” it is clear based just on the first few lyrics that the noise-pop duo has changed immensely: “Heard you say suicide in your sleep / just get on with it / you were born to lose.” This is no longer the band that wrote entire songs consisting of nonsensical lyrics like, “Got my A machines on the table / got my B machines in the drawer.” Sleigh Bells has added depth to the blaring potency that made them famous. While “Reign of Terror” is not as instantly stunning as “Treats,” the sophomore effort exhibits a new maturation.

“Reign of Terror” may lack instant pop appeal, but the album more than makes up for this deficiency in its craft and production. Miller described “Treats” as “party music.” In contrast, “Reign of Terror” is laden with heavy emotion. The shift makes sense: Just before the release of “Treats,” Miller’s father died in a motorcycle accident, and while the band was touring later that year, his mother was diagnosed with cancer.

The album appears to be Miller’s attempt to deal with these tragedies. Its emotional tenor careens wildly, from suicidal to hopeful to wistful to furious. “End of the Line” seems to be written from the concerned, sympathetic perspective—perhaps Krauss’s own—of someone watching a friend grieve: “Just try and talk / you’ll do anything, but you’re never gonna keep it down,” she sings. “Leader of the Pack” borrows its title and chord progression from a 1964 song by the Shangri-Las about a motorcycle accident. It features the simultaneously despondent and cathartic refrain, “Don’t you know he’s never coming back again?” And even “Demons,” which gets closest to face-kicking levels of raw energy on “Treats,” is tinged with righteous anger. The first half of the album does an impressive job of communicating these volatile emotions without indigestible moroseness.

Unfortunately, the album’s back half starts to sag under the weight of too many mid-tempo power ballads. Krauss’s vocals are normally compelling because of her ability to switch effortlessly from a shoegaze coo to a stadium-rock scream, but in the album’s last few tracks, she settles too comfortably into the former. Tracks like “You Lost Me” and “Never Say Die” are mesmerizing on their own, but they begin to bleed together when placed side by side. The energy of earlier tracks is nowhere to be found, and this monotony means that many people will probably stop listening after “Comeback Kid.”

This is unfortunate, because the last four tracks are full of creative arrangements and compelling lyrics. The album’s bleakest track, “D.O.A.,” is built around a plodding guitar, and “Road to Hell” captures the conflicting emotions of someone who wants to be left alone but desperately needs the support of other people: “Don’t run away from me, baby / just go away for me, baby.”

Ultimately, “Reign of Terror” won’t be blasted out of dorm room stereos nearly as much as its predecessor. But it wasn’t meant to be. “Reign of Terror” proves that Sleigh Bells can still slay.

—Staff writer Matthew J. Watson can be reached at matthewwatson@college.harvard.edu.