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When the Durham duo Midtown Dickens released its debut, Oh Yell!, in 2007, the music reflected the city that members Kym Register and Catherine Edgerton had always called home: charmingly familiar, but with a layer of tough, post-industrial grit; steeped in history, but invigorated by modern renovations. Midtown Dickens, after all, had learned to play on the fly with whatever instruments they could scavenge or borrow. They soon turned out infectious ditties informed by punk’s DIY spirit, bluegrass’ conversational instrumentation, folk’s storytelling traditions and the emotive crunch of the blues (itself a part of Durham’s historic tangles). As a child, Edgerton sat in on her father’s front-porch bluegrass jams, and that spirit of informal community music-making pervaded Midtown Dickens’ songs, too. Their spare, inviting spaces encouraged sing-alongs from the start, in whatever key one preferred.

Their sophomore album, the self-released Lanterns, retains these core values while benefiting from the lucid production of Scott Solter and an expanded cast of players. While their debut featured many auxiliary musicians, the duo has expanded into a permanent quintet. Will Hackney, of Trekky Records and Lost in the Trees, contributes backing vocals, mandolin and cornet. Jonathan Henderson and Michelle Preslik add a multi-instrumental bonanza, including electric guitar, percussion, upright bass, piano, accordion and glockenspiel. But the rich voices of Register and Edgerton remain at the center, the former loamy, the latter glinting with brass. At times, it’s like listening to Janis Joplin duet with Loretta Lynn, collapsing a divide between lush soul and flinty country. Their voices intertwine and explode into uproarious refrains, Edgerton often lifting into raggedly perfect harmonies.

The new members broaden the potential for subtleties of arrangement, though. The rollicking chords of “Old Dogs,” for instance, crest on woozy horns, crash-land in a scattering of chimes and peter out to reveal what sounds like a singing bowl ghosting behind them. The subdued “The Road (Pt. 1)” unfurls on a slow, dark tide of droning bass and cheerless piano. The weary uplift of its massed vocals is among the album’s most arresting sounds. These inventive flashes paint lyrical imagery: On “The Fish Song,” an odd number narrated by a dead fish aboard a carousel, an accordion evokes the tired wheeze of an old calliope. And on the dusty-trail country song “It’s Alright,” Edgerton’s singing saw wafts up like a lonesome cowboy’s whistle on the high plains.

Without sacrificing the sense of spontaneous fun that makes many of its songs worth a dozen drably proficient indie rock curtsies, Midtown Dickens has started to take their music a bit more seriously. A band that once was wont to sing about Tetris now seeds genial surrealism with substantial human transactions. It’s as if the group’s increased musical proficiency gave them the confidence to lay more on the line lyrically, too. They play better, sing better, say better.

This modest increase in professionalism is relative. In an era when technology is geared toward lassoing music into sterile perfection, Lanterns celebrates the beauty of the flaw. Inspired imperfections add vibrancy. All over Lanterns, fissures offset the mediated feeling of the taped musical experience. Tempos drag and then lock in passionately. Vocal lines drop and rush back in. Edgerton’s line-ending “woo-hoo’s” on “Old Dogs” fall unevenly across the beats, like afterthoughts. The result lacks any sense of the foreordained, seeming to invent itself in each moment.

Such sanctity of the imperfect is writ large in the lyrics, too, which often blend a sort of good-natured snark with a spirit of forgiveness, or acceptance. “I’ve been too hard on you,” Edgerton and Register duet on “Just Like Me,” in an off-center roundelay. And on “Annihilation,” Register sings, “It’s not your fault that you bore me/ I must be naive/ For thinking conversation should be interesting.” This band’s long let itself fuck up. Now they’ve learned to allow others to fuck up, too. They don’t gloss over failings and disappointments. They let them be and sing them into songs. You can sing them, too.

Midtown Dickens releases Lanterns at Duke Coffeehouse Friday, Aug. 28, at 9 p.m. Mount Moriah and Des Ark open the free show.