Growth is often incremental and on the surface, the Spider Bags don't sound as if they've changed much on their fourth album, Frozen Letter, even though it marks their debut on a new (and bigger) label, Merge Records, and their first effort since guitarist Gregg Levy moved from full-time to part-time status with the group, appearing on just four of the album's eight tunes.

But give it a couple of spins and Frozen Letter does sound tighter, more ambitious, and more mature than the band's earlier work, with less of a focus on bad behavior and more observational material that suggests Dan McGee and his bandmates are doing less drinking and more thinking lately.

While the first half of the album is devoted to short, garage-inclined bursts like "Japanese Vacation" (smart and swaggering, with some fine, clean picking from frontman McGee) and "Summer of '79" (a nervy rant against classic rock that asks the question "Why do you wanna be a Rolling Stone?/Why do you think your daddy is the King of Rock & Roll?"), the album closes out with four tunes that all run over five minutes, and "Coffin Car" and "Walking Bubble" both manage to sound simple but contemplative, the latter dominated by acoustic guitars and a dour vocal, while the former feels impressionistic and just a bit artful, full of shimmering tremolo, ambient electronics, and thick organ patches alongside guitar figures that grow bigger and noisier as the melody moves forward.

The extended pieces that close out the album make Frozen Letter less immediately engaging than 2012's Shake My Head, but if this set isn't much of a party, it confirms the bandmembers are getting smarter and more creative, and while early in their career Spider Bags didn't seem like a band that would welcome maturity, these songs show they're growing into it in their own slightly sloppy way.