Madison Square Garden

It’s about four hours into the Z100 ­Jingle Ball when Fall Out Boy lean into “This Ain’t a Scene, It’s an Arms Race” and roughly 20,000 pre-to-postpubescent girls unleash a howl of consensual desire. FOB bassist Pete Wentz—wearing a ski-boot-sized cast on his broken left foot—responds with a quarter-salchow. But the furor isn’t about Fall Out Boy. Jonas Brothers have been spotted offstage, and they’re on next.

The annual holiday concert thrown by New York’s dominant Top 40 radio station is an all-stars-on-deck gala: the reigning American Idol, Jordin Sparks; Alicia Keys, who has this week’s No. 1 hit; Timbaland, the production genius who has owned the charts for two years. And the crowd greets each luminary by catching up on their text messages. Genuine, ear-rattling excitement arises only for brief video teasers ­projected between acts, showing the Jonases—the shaggy-haired, sunken-chested lords of Radio Disney—romping on their tour bus.

Otherwise, the crowd mostly seems unimpressed. Sparks’s catchy single ­“Tattoo” inspires a sing-along. Avril Lavigne (resplendent in spangled skate-rat pants and ­matching hi-tops) whips things up with the ­cheer-punk thump of “Girlfriend” but loses the crowd with 2002’s “Complicated,” which in the shelf life of radio may as well be an oldie. Backstreet Boys’ 15-minute set is ultra-smooth, but watching them croon “Everybody (Backstreet’s Back)” and labor through decade-old choreography is almost unbearably poignant. Nobody in the building knows better than Backstreet how psyched Jonas Brothers are—or hates them more.

Comic relief arrives in the hulking form of Timbaland, who launches into a ­mesmerizing monologue, introducing his 5-year-old son (“Daddy loves you. And you love Daddy”), unleashing Yogi Berra–­worthy aphorisms (“It’s been a great year for me these last two years”) and, finally, pandering (“I want to work with the Jonas Brothers”). He also brings on his protégés OneRepublic­, declaring, “I always wanted my own Fray.” Such small dreams for such a big man.

Finally it’s time for the main attraction. Nick, Joe and Kevin Jonas (ages 15, 18 and 20) arrive amid geysers of sparks, wearing ’70s shag haircuts and wielding mildly catchy choruses of similar vintage. Their merely serviceable performance does display a whiff of novelty: Previous teen pinups offered a safely sexy take on contemporary sounds, but Jonas Brothers are the first ones to fetishize pop’s past.

So how did they end up headlining a bill crammed with hitmakers? They did it the Disney way. As the record industry continues to crumble, the future may look like the Jonases: cute, multi-platformed and backed by the promotional muscle of The Mouse. They’ve been the opening act on the Hannah Montana tour, and where she, the Cheetah Girls and High School Musical all broke first on TV, the Jonases are huge even without the tube. That will soon change. “Be sure to check out our new TV show,” Joe Jonas says to the night’s biggest cheers. “It’s coming next year on the Disney Channel!”