Three years ago, London folk-rock quartet Mumford & Sons blew up in a major way with "The Cave," an angst-fueled, Grammy-nominated strummer built on quiet-loud dynamics, Country Marshall's propulsive banjo, and Marcus Mumford's gruff bellow, which churned like a locomotive in free-fall. Perhaps a tad overwrought, but also pretty tough not to love, that track established a blueprint for the "West London Folk" revival that blossomed around the decade's turn. Problem is, Mumford & Sons have re-written "The Cave" — with very minor embellishments — about 25 times. Babel, the band's sophomore album, doesn't fuck with the formula one bit, offering 12 more trademark tracks blending snotty punk aggression with bluegrass instrumentation and spiritual, MFA-hopeful lyric strain. Taken in bits and pieces, it's still nearly impossible not to be moved by the bombast, even if the catharsis feels inevitable, not earned. "I stretch my arms into the sky," Mumford sings on "Babel" in a full-throated rage — like a man desperately in need of a lozenge — as acoustic guitars and banjos push the tension past the breaking point. On the bluegrass shuffle of "I Will Wait," the quartet's glowing back-porch harmonies build into a massive, staggering wall of sound. Elsewhere, there are bits and pieces of color contrast (the tense piano on "Whispers in the Dark," brass interjections on "Holland Road"); but as a whole, Babel is frustratingly monochromatic and laughably precious (sample lyric from "Hopeless Wanderer:" "I was still, but I was under your spell/When I was told by Jesus all was well/So all must be well"). Individually, these songs pack an emotional wallop, performed with a passion that is rare in today's indie-rock scene of disconnected cool. But taken as a giant lump, they're exhausting dead-ends: 12 straight climaxes cancel each other out — and Babel could use a little rising action.