"I've noticed something," said Good Charlotte's Benji Madden as he looked out over the Tweeter Center last night. "There's a lot of girls here."

It wasn't the most perceptive observation (and, in truth, no more than a way to segue into the band's song Girls & Boys"), but there wasn't much room to disagree. The sold-out crowd for the Jingle Ball was overwhelmingly female and largely adolescent. If you were looking for a babysitter last night, you were out of luck.

Featuring a half-dozen acts linked only by their popularity, the concert rounded the music bases. There was the pop-punk of Good Charlotte and Avril Lavigne, hip-hop from Timbaland and Sean Kingston, and finalists one and two from this year's American Idol, Jordin Sparks and Blake Lewis.

There was little in the way of musical cross-pollination, although Timbaland gave a slice of his set over to the soft-rock band OneRepublic, whom he referred to as "my Coldplay." (The similarity is impossible to miss, but you have to wonder how they felt about being tagged as copycats in front of a crowd.) After swooning their way through "Apologize," whose souped-up Timbaland beat counters some of the song's lugubriousness, they went on to play an off-the-cuff version of "Stop and Stare" with Timbaland beatboxing underneath, and then swapped roles to back him on "Throw It on Me."

The brief collaboration didn't produce sparks, but it improved notably on the beginning of Timbaland's set, which found him half-heartedly rapping along with the recorded versions of his Nelly Furtado duets, "Promiscuous" and "Give It To Me." On several occasions, his performance consisted of standing off to the side of the stage and nodding his head as his DJ unveiled some new production of his, including a forthcoming collaboration with Madonna and Justin Timberlake.

But if there was something odd about paying to watch a producer listen to his own records, it didn't seem to strike the audience that way. It didn't seem to matter who -- if anyone -- was performing, as long as the songs were good. They were as happy to dance to the music that came over the P.A. between sets as to watch anyone on stage.

A market researcher with an applause meter could have made some valuable determinations. Sean Kingston's reggae-lite ballads pushed the needle into the red, but the singles from Avril Lavigne's new album drew a noticeably more muted reaction than past chart-toppers. The bizarre intro to "Losing Grip," which quoted Led Zepplin's "Kashmir" while dancers clad in black body suits and white face masks spun around the stage, mixed a dash of stage show with Lavigne's trademark faux punk. Considering that many of her fans aren't old enough to gamble, she might do well to cut back on the Vegas schtick.