On its fourth album, the avant-pop band tries to capitalize on its critical cachet.

After a pair of albums that featured slow-moving, elegant soundscapes often stretching past the five-minute mark, Grizzly Bear finally released a brash, catchy single in 2009 that turned the members of the unusual quartet into unwitting indie-rock stars.

"Two Weeks," the lead single off the Warp Records band's third album, "Veckatimest", was a piano-driven bit of baroque pop that wound up in a handful of films and TV ads, most notably a Volkswagen commercial that aired in 2010 during Super Bowl XLIV. The track has sold 225,000 copies, according to Nielsen SoundScan, with its music video garnering 6.4 million views on YouTube.

"When we did 'Two Weeks,' we were excited to have a song that was more fun than things we'd done in the past," guitarist/vocalist Daniel Rossen says. The single, and critical praise for "Veckatimest", helped deliver a No. 8 debut for the album on the Billboard 200 in May 2009. Three months later, Grizzly Bear got a high-profile shout-out from Jay-Z as "an incredible band" in an MTV interview.

So how will Grizzly Bear capitalize on its newfound "cool factor" for "Shields", its fourth full-length due Sept. 18? Warp label manager Josh Berman believes the album will "expand [the band] in as many directions as possible...and try to reach outside the indie-rock world."

Even with multiple TV appearances lined up and synch opportunities in the offing, it's an admittedly tall order. "Shields" is a grittier album than its predecessor, with hooks that slowly reveal themselves underneath more muscular arrangements.

"It's not like a pop record by any means," Rossen says. "There's some accessible stuff on this record. There's also some really crazy stuff."

After touring for a year behind "Veckatimest" and then taking a year off, Grizzly Bear -- Rossen, vocalist/guitarist Ed Droste, bassist Chris Taylor and drummer Christopher Bear -- reconvened in June 2011 in West Texas, a departure from its usual recording spot in Cape Cod, Mass. The band opted to stay in an old army barracks that didn't have air conditioning, looking for some new inspiration in the Texas desert.

The heat proved so extreme the group simply couldn't work during the day. After a month of sweltering late-night recording sessions, the band produced 11 new songs, but eventually kept only two tracks and scrapped the rest. "It took us a little time to find our stride," Rossen says. Grizzly Bear took another break, allowing Taylor to release a solo album under the moniker CANT last September, then retreated back to Cape Cod to start over on "Shields" earlier this year.

Instead of delivering what Berman calls a "trickle-out" album announcement, Warp unveiled "Shields"' release date, revealed Grizzly Bear's fall tour dates, shared lead track "Sleeping Ute" and made album preorders available on June 6. As a result, the band's name became a trending topic worldwide. "Sleeping Ute" wasn't positioned as the official single but, according to Berman, the strong reaction to the winding rock track caused Warp to service the song to triple A, noncommercial and college radio upon release. While the song has sold 12,000 downloads, according to SoundScan, the actual first single, "Yet Again," arrived in early August, serving as the focal point for TV and radio performances.

Grizzly Bear performed both songs and "Two Weeks" on "The Colbert Report" as part of the Comedy Central host's StePhest Colbchella music festival on Aug. 14, which also featured the Flaming Lips, fun. and Santigold. The performance onboard the USS Intrepid marked the band's first live show in two years, a calculated risk to gain a wider audience more than a month prior to "Shields"' release.

"We saw really nice spikes, both on preorders and iTunes sales of already released tracks, as well as general awareness," Berman says. "On the Colbert website, you'd see people commenting, 'I love the Flaming Lips and fun., but I've never heard of this Grizzly Bear band and it's amazing.'"

As the group prepares for an international headlining tour that starts Sept. 16 in Nashville and reaches Europe on Oct. 16, Warp is readying an intensive iTunes campaign: a single of the week has been pitched but not confirmed, and an iTunes 360 campaign, which features iTunes-tagged banner ads on dozens of different outlets, will be rolled out with the album. Meanwhile, the release will also get airplay in Starbucks stores, and Grizzly Bear will grace at least two late-night talk shows before the end of the year.

As for a flashy follow-up to the "Two Weeks" Super Bowl ad, Warp is trying to stay aggressive. "There's been some nibbles, and we're really pushing our synch teams," Berman says. "You can never predict these things. It's only a matter of time."