It's not hard to understand why fun. is a front-runner at the Grammy Awards ceremony on Sunday in Los Angeles.

The band with the kooky stylized name, which happens to be the only act nominated in each of Grammy's so-called Big Four categories this year, crafts easy-to-digest pop-rock ditties that leave no bad aftertaste. Actually, most of them leave no aftertaste at all.

The majority of the tunes from the band's rather thin songbook just hit you with big hooks and choruses and then seem to vanish into thin air. Yet they are indeed fun while they last.

On Thursday night at the Fox Theater in Oakland, fun. delighted the sold-out crowd, which apparently drew strongly from the local junior high schools. What concertgoers got was the musical equivalent of cotton candy -- sweet yet somehow unfulfilling in some ways.

There were some exceptions. "We Are Young" and "Some Nights," which is the title track to the band's breakthrough sophomore effort, were both terrific. The former is one of the best pop anthems of recent years and seems destined to win the Grammys for both record and song of the year.

Yet the concert also illustrated why the New York City band shouldn't win the album of the year Grammy, even in a weak field that also includes such mediocrities as Jack White's "Blunderbuss" and Mumford & Sons' "Babel." And can someone please explain to me why a group that released its debut record in 2009 ("Aim and Ignite") is even eligible for the best new artist Grammy in 2013?

Fun. is definitely having a hard time living up to its own soaring popularity, and it's quite understandable why the band is showing signs of growing pains, which mainly come from trying to stretch maybe 40 minutes of worthy material into a 90-minute headlining set. But give this trio -- lead vocalist Nate Ruess, guitarist Jack Antonoff and multi-instrumentalist Andrew Dost -- some time and it could turn out be as good onstage as it is on the radio.

It will be interesting to see how fun. does when the band returns to the Bay Area to perform at the much larger Greek Theatre in Berkeley on Sept. 6. Tickets for that show go on sale Feb. 15 through Ticketmaster.

Backed by three side musicians, fun. nicely blended the material from its two albums at the Fox. The band's studio albums are quite different, with the first being the more adventurous and slightly psychedelic of the pair. But fun. has updated all the old tracks onstage so that they sound like they'd fit on the newer album ("Some Nights").

The first half of the set list was filled with place holders -- tracks that chewed up time while we waited for the good stuff. The band opened with "Out on the Town" (a bonus track from "Some Nights") and then coasted through such inoffensive offerings as "At Least I'm Not as Sad (As I Used to Be)" and "The Gambler," both of which hail from "Aim and Ignite." The band showed its boy band side with the One Direction sound-alike "All the Pretty Girls" and then was a complete Coldplay clone on "Stars." Best of all, it was pure fun. on "We Are Young."

Yes, as the band's biggest hit declares, they are young. But give fun. some time and the band could truly mature into something special.

Follow Jim Harrington at Twitter.com/jimthecritic, Facebook.com/jim.bayareanews and http://blogs.mercurynews.com/aei/category/concerts.

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To see a slideshow of Thursday's concert, go to www.mercurynews.com/entertainment.