Despite the myriad of comparisons that suggest otherwise, Bloc Party is not punk. They’re not really post-punk, either. Even after they were inevitably shot down and tagged with the “younger, hipper Gang of Four” label upon the release of their excellent, 1979-esque 2005 debut “Silent Alarm,” it still never quite fit.

Bloc Party could not have been christened any of these things simply because they’re too earnest, too thoughtful, and their music too Ö well, flawlessly constructed. They’re not sloppy. They think things through. And they’re sensitive, almost to the point of naivety. They’re refreshingly un-self-conscious, if not strongly convinced of their ability to say something significant.

Their sophomore album, “A Weekend in the City,” reinstates all of these things, while showing a newly developed punk streak in their attitude. Despite an age where sincerity is scoffed at, Bloc Party refuses to back down.

The music follows the same unflinchingly ambitious aesthetic. Bloc Party cares just as much about incorporating all the far-reaching possibilities within pop rock, and if they want to orchestrate it through means of arena-worthy hooks or grandiose, epic balladry, by God, they’ll do it.

Overall, “A Weekend in the City” is darker, broader and wears more hearts on its sleeve, which is somewhat of a departure from “Silent Alarm.” It relies less on the group’s youthful brand of fidgety dance-rock and more on frontman Kele Okereke’s specific, anguished storytelling on life in London’s postmodern urban jungle as his central concept, which he thankfully approaches with a mixture of tension and confusion, and not a glossed pretension.

Opening track “Song for Clay (Disappear Here)” has the powerfully piped Okerere trying on a slightly silly falsetto, whispering his longing to “be heroic in an age of modernity” and “dazzle them with my wit,” while backed by quivering keyboards and a hushed electric strum. It seems a slightly meek start, but within a minute the band wreaks familiar havoc with stomping drums and a fuzzy, pulsating air raid of guitars that pushes its way to a chorus all at once infectious and thrilling.

“Waiting for the 7:18” employs a similar pattern (and serves as an excellent summary of Bloc Party’s audacious, halcyon personality): with fluttering piano plinks, it starts unabashedly starry-eyed; but slowly melts its way into fiercely gallant guitar and richly layered harmonies built well for humane lyrics like “Sitting in silence in bars after work/ I’ve got nothing to add or contest/ can still kick a ball a hundred yards/ we cling to bottles and memories of the past” and “If I could do it again, I’d climb more trees/ I’d pick and I’d eat more wild blackberries.”

Okereke’s booming, all-encompassing vocals radiate plenty of sensuality alongside all that sobriety, particularly when carrying an uncharacteristically woozy ballad like “Kreuzberg,” where the bitter taste of a string of flings makes him question “What is this love?/ Why can I never hold it?/ Did it really run out in those strangers’ bedrooms?” Moods like that, draped in a blend of desire and ambivalence, are part of what makes “A Weekend in the City” so accomplished.

Often times, though, the album falters under Bloc Party’s near-abuse of the histrionic. Certain songs in the second half shoot for slick mainstream appeal but come off confusingly outdated, something that would have felt like, so heavy, man Ö in maybe the mid-’90s. “Uniform” attempts to lecture the youth on modern apathy through a swarm of irritating synth, but the song’s overblown seriousness turns the message into comedy.

Though scarce, these clunking, unthreatening moments feel more like a “whatever, mom and dad!”-type resistance, and weigh down the more intelligently addressed current issues (xenophobia, drug use, international conflict) found elsewhere on the album.

Nevertheless, “A Weekend in the City” is still an impressive collection of brashly energetic, relevant songs that candidly shift from alienation to connection to hope and back again.