The faces are fresh, but not the ideas

ROCK always needs new generations of fans to survive. So it was an impressive, epic feat that five young bands headed by Fall Out Boy and the All American Rejects filled the Los Angeles Sports Arena on Tuesday with thousands of excited new listeners.

Less rewarding was the music itself: market-tested emo-pop uncontaminated by fresh ideas. It is a genre related to punk but mostly detached from its anti-establishment tradition, and is known more for its parade of cute boys in eyeliner, spiky hair and tattoos just so.

It is to punk rock what ‘80s hair-metal was to hard rock: all showbiz and makeup and a few catchy tunes, with nothing that will survive past this blissful moment. Which is cool when you’re 13. So let the kids have their fun. It is rock’s current growth industry.

The latest indie album from support act Hawthorne Heights, on indie label Victory Records, sold about 100,000 albums its first week alone. And Fall Out Boy’s newest, “From Under the Cork Tree,” is a modern-rock crossover hit. But at the Sports Arena, Fall Out Boy suffered from blurry sound and the sameness of its repertoire, from “XO” to “Dance Dance.”

Between songs, bassist-lyricist and sometime exhibitionist Pete Wentz did all the talking, rambling on about sex and sex and sex and sex. But a few dozen nasty words aside, Fall Out Boy was as safe and dumb as Ivory soap, and far less interesting.

Then came a rallying cry for a new generation of rock rebels: “Who wants to stay young and never grow old? Who wants to stay up all night and sleep all day? Who wants to see Kelly Clarkson’s video knocked out of No. 1 with this song?!” Fall Out Boy’s priorities were never in doubt.

All American Rejects came off pretty well by comparison, bouncing to the lively slashing pop-punk of “Dirty Little Secret” and “Move Along.” Originality wasn’t the point here either, but singer Tyson Ritter at least remembered punk’s communal side by inviting fans to call friends outside the arena on their cells to share the next song -- free of charge.