Could it possibly be a coincidence that the first song on Infinity On High, Fall Out Boy's follow-up to their smash second album is called ''Thriller,'' the title of Michael Jackson's ne plus ultra of pop blockbusters? No, it couldn't: With these perpetually arch emo kingpins, you can be sure all music-biz in-jokes are intentional. The song, belted out by singer Patrick Stump over caffeine-charged punk-pop guitar jolts, is a meditation on Fall Out Boy's favorite theme, Fall Out Boy, that mixes paeans to loyal fans (''Our hearts beat for the diehards'') with what is either a parody of rock-star grandeur or the genuine article: ''I can take your problems away with a nod and a wave/Of my hand.'' The guy yammering over the song's opening strains? That's Def Jam president Jay-Z, Fall Out Boy's pal another reminder, for those who may have missed the point, that the little band from Chicagoland has graduated to the ranks of pop royalty.
Fall Out Boy have reason to gloat. The theatrical and irreverent third-generation emo that they pioneered has become a certifiable subgenre, inspiring hit acts like their protégés Panic! At the Disco. But Infinity proves they're the masters of this peculiar art. The guiding force is bassist-lyricist Pete Wentz, responsible for ''You're Crashing, but You're No Wave,'' ''The Carpal Tunnel of Love,'' and other exuberantly pun-filled songs that both wallow in and lampoon emo angst. ''A penny for your thoughts/But a dollar for your insides/And a fortune for your disaster/I'm just a painter... And I'm drawing a blank,'' Stump sings in the galloping power-pop blast ''Don't You Know Who I Think I Am?'' Like all Fall Out Boy lyrics, it's not quite as clever as Wentz seems to think, and his obsession with posers, lame ''scenes,'' and, above all, his own band might annoy listeners not currently enrolled in high school. But Wentz's words have a pleasing vernacular spunkiness this is the Esperanto of young American suburbia, poetry of the mall and the chat room. Who but Wentz would brag, ''Every dotcom's refreshing for a journal update''?
Of course, it's the loud, jagged sound that really moves the kids. FOB's guitars still blare, and Stump has evolved into a superb frontman, with a voice that slides supplely from a bratty punk bark into a honeyed falsetto. But the pleasant surprise here is the band's new sense of swing: Several songs, including the hit ''This Ain't a Scene, It's an Arms Race,'' dip winningly into R&B, a move aided by co-producer Babyface. Lo and behold, it turns out these pasty emo boys are a pretty great blue-eyed soul band. Infinity ain't exactly Thriller but Maroon 5 better watch their backs. A-