"Push it push it push it!" Alexis Krauss shouts at the beginning of Reign of Terror, and that's exactly what she and Derek Miller do on their follow-up to Treats.

Despite its in-the-red volume, Sleigh Bells' debut was a fragile, almost alchemical blend of wispy melodies and crushingly heavy beats and riffs.

How could they top an album that was already turned up to 11? By turning things up to 12: on Reign of Terror, the duo brings the nods to metal that added a headbanging thrust to Treats to center stage.

From the album's name down to song titles like "D.O.A." and "Never Say Die," Krauss and Miller allude to metal's flirtations with death, which makes a strange kind of sense: Treats was a blend of sounds that shouldn't have worked but did, and changing that formula is riskier still.

Oddly, though, the duo sound more gimmicky with a narrower focus than they did when they were tossing drumline beats and P-Funk samples into the mix.

With Miller playing a shred and squeal-friendly Jackson USA Soloist and a slicker production, Reign of Terror has a chilly, harsh edge that makes Sleigh Bells' debut sound downright quaint by comparison.

Despite the album's hyper-saturated sound, everything feels more polarized; Krauss' vocals are often more sugary than ever, and next to Miller's guitar heroics, it often feels like a hesher giving his chops a workout while someone blasts teen pop next door.

The duo's alchemy resurfaces on the songs that sound the most like Treats: on "Crush," Krauss sounds like a revolutionary cheerleader toying with a captive enemy when she sings "I've gotta crush you now"; "End of the Line" echoes the Treats' hit "Rill Rill"'s breathy pop poses; "Leader of the Pack" boasts a tooth-rottingly sweet melody, and "Comeback Kid" balances the album's heaviness with humor and finesse.

However, when the band goes deeper into metal territory, they aren't always as successful: The aptly fiery "Demons" sounds extra-vengeful with strutting fretwork and rapid-fire kickdrums, but "Born to Lose" and "Road to Hell" just get weighed down with heavy riffs.

Indeed, Reign of Terror falls off precipitously when the guitars overtake everything else, as on the album's meandering last three songs.

Miller and Krauss deserve credit for branching out and taking risks, but as the album veers back and forth between inspired and irritating, and as they scramble to fill every nook and cranny with some type of sound, Reign of Terror ends up being a fatiguing reminder of how remarkable a feat Treats was.

Sleigh Bells may have topped themselves here, but it's a case of more being less.