It’s sad when the filmmaker best attuned to behavior patterns of 21st-century teens has made only two films in the 21st century.

Peter Sollett’s 2002 feature-length debut, Raising Victor Vargas, was a teen romantic-dramedy that reveled in realistic details. Given its acclaim, it seemed inevitable he’d be plucked for fresh spins on studio work.

Six years later, Nick and Norah’s Infinite Playlist is just Sollett’s second film and about at the same level of quality, albeit slicker, as Victor. Consider him an indirect benefactor from the Judd Apatow brand, although that ubiquitous writer / producer / director has no direct involvement here.

Pineapple Express did nothing to prove why Apatow handpicked indie-drama directors like David Gordon Green for big-studio comedies. But Nick and Norah does — unassailably authentic in a way Diablo Cody could only imagine, sweetly romantic, thrillingly evocative of New York nightlife and proof Kat Dennings, as Norah, could become the next Diane Keaton.

Nebbish bassist Nick (Michael Cera) is the rhythm section for The Jerk Offs, a band without a drummer. But he’s off his romantic groove, shaken after being dumped by popular girl Tris (Alexis Dziena) and coping by making mix CDs for closure.

Of course, Tris usually passes along discs like Road To Closure: Vol. 12 to Norah, a musical kindred spirit to a boy she’s never met. Or so the film would like us to believe. The only real flaw is a big one: There’s no way Norah never would have met Nick in six months of his dating Tris.

Norah barely tolerates Tris, but fears how Tris might spread misconceptions of her social activity. When Tris (with new boyfriend in tow to torment Nick) spots Norah alone at a Jerk Offs show, Norah pretends Nick is her boyfriend — to his surprise and Tris’s chagrin.

Soon, Nick and Norah are puttering around New York in the wee hours of the morning — both seeking to find a secret show from a hot indie band, Norah’s drunk friend Caroline (Ari Graynor) and, most importantly, a confidant in whom to confide.

Cera plays a more assertive variation on his Juno and Superbad characters, but that’s like saying Dane Cook is at his most romantic in My Best Friend’s Girl. Cera excels at jangly-nerved teens, but it’s time for him to branch out.

After this and Charlie Bartlett, it’s been a banner year for Dennings., with her modest neuroses identifiable and her charm compelling.

Sollett revisits the same attention to specifics as in Victor: Nick’s nervous deletion of an important voicemail message; his Cure ringtone; the inflection of Caroline’s slurred, drunken apologies; random phrases becoming perfect band names.

Moreover, it’s in the legitimately teenage dialogue first-time writer Lorene Scafaria adapted from Rachel Cohn and David Levithan’s novel. Nick and Norah are verbose and witty, but not vogue hipsters beyond their years. They’re just culturally informed.

Scafaria and Sollett also enhance and elicit a winning wisdom. Leaving teen love behind isn’t cause for celebration, or even a slight smile. It’s bittersweet, it’s empowering, it’s learning from a mistake. It’s growing up.

Nick and Norah’s Infinite Playlist legitimately dramatizes those unexpected, unforgettable nights where the hours, and memories, run together. The movie finds its outstanding soundtrack from mp3 blogs, but finds its soul in the two-second spaces before a mix CD goes on to the next track. On those terms, the last cut of Nick and Norah is a killer and sure to leave you with a giddy glow.