AFI bonds with 12,000

Momentum isn’t always an easy thing to read in pop music. By one measure, Northern California rock band AFI is on the downswing, its new album selling barely half the million-plus total of its predecessor, the 2003 commercial breakthrough “Sing the Sorrow.”

But there are ways for a band to weather these shifts. One is to take as much sustenance as possible in those pockets where support is undiminished and to remind yourself that the bond with fans might matter more than sales figures.

So it was for AFI at the Long Beach Arena on Friday, where everything seemed triumphant. The sellout crowd of 12,000 bespoke AFI’s popularity in the L.A. area, where its “Miss Murder” is the most-played song on the top modern-rock radio station, KROQ-FM (106.7).

Actually, a bit of rejection suits AFI, a band that presents itself as a refuge for outsiders and the misunderstood. Its community of committed fans is called the Despair Faction, and the new album’s title, “Decemberunderground,” suggests a deep, dark hiding place.

The band is open-armed, open-hearted, vaguely messianic, in a manner that evokes bands as various as U2, Depeche Mode and the Cure.

“I promise you my heart, just promise to sing. / Kiss my eyes and lay me to sleep,” Davey Havok sang Friday, beginning the concert with the prelude that opens the new album. Havok, a buff vegan with an edge of androgyny, is the face of AFI (it stands for “a fire inside”), and though he lacks the larger-than-life charisma of rock’s most compelling frontmen, he knows how to stoke that strong emotional connection with the fans.

He also appears to like the flair and drama of Freddie Mercury, and during the first encore, the power ballad “God Called in Sick,” he stepped off the stage and into the crowd, where he stood on their upraised hands as he sang.

For a guy who can say, during one of his profuse thank-yous to the audience, “We love you [pause] and we dance,” Havok was actually pretty down-to-earth (as were his three bandmates), with all the raised-arm grandiosity maybe a residue of AFI’s long service on the indie punk scene in the 1990s.

Punk remains a strong element in a sound that’s absorbed all sorts of other influences, from goth to glam to pop, and while the music can be inventive and surprising on record, AFI seemed out of its element in the arena setting Friday -- at least this arena, one of the oldest and most echo-heavy in the Southland.

Try as it might, AFI couldn’t crank things to liftoff level, and the sound remained thin and tepid, without the presence and force that can enlarge and intensify emotions to a vivid, inescapable scale.

That kind of emotional impact has rarely been a problem for AFI in clubs and theaters, and this same set probably would have been vastly more effective in a room half the size and with better sound.

If the band’s following is really downsizing to a smaller, loyal core, the band is less likely to face the challenge of making it work in arena settings.

Few performers enjoy seeing their audiences shrink, but that would be a great silver lining for AFI, not to mention the Despair Faction.