In their eight-year existence, raucous indie-pop act Tilly and the Wall managed, quite surprisingly, to escape the narrative written by their marketing squad: Despite their Nebraska roots, they shared few sonic similarities to Rilo Kiley or The Faint. Despite their most prominent feature — a tap-dancing percussionist — they managed to avoid feeling like a Yellowcard-esque novelty, thanks in part to several excellent tracks. (Namely, “Sings Songs Along” and “The Freest Man.”) And when Tilly and the Wall’s most frequent descriptors — exuberant, playful, childlike, or any other adjectives associated with American twee — became trite, they expanded their musical vocabulary to worldy. Aggressive. Garagey. Not Yellowcard.

The thing that eluded the band (and their side projects, such as Flowers Forever and Icky Blossoms), though, was a definitive work. And if Heavy Mood is any indicator, that moment isn’t coming, though it’s not for lack of trying. Tilly establishes plenty of goals — riot grrl (“Love Riot”), Spector-riffic girl-pop (“All Kinds of Guns”) and dance-rock (“Defenders”) — but the LP fails to hit all targets. Instead, as a collection, this feels bloated and manic; and unlike Bottoms of Barrels and O, which possessed occasional adrenaline rushes, Heavy Mood feels amorphously mediocre.

Worse still is their reliance on ill-fitting nu-indie tropes: Their obsession with youth (illustrated on, uh, “Youth”) seems, after a near-decade of treading in these waters, suddenly disingenuous. It’s further amplified on the cringe-worthy, faux-motivational “I Believe in You” — seriously, that’s the song’s title — which, as Metric, feels like a tween-pop cash-grab. The band, in their late-’00s salad days, crafted some delectably scrappy modern twee; but, as they sing on Heavy Mood, “we cannot stay this way forever.” Perhaps it’s a sentiment that, in 2012, Tilly and the Wall should take more seriously.