Inside, just after dusk, ushers and security types wearing dark suits are in place to both police (again, no cameras or smartphones shall be hoisted during the performance) and ferry everyone to and from their assigned, segmented, surprisingly spacious floor sections. A few minutes after 6 p.m., the house lights die and a sheet of low-end noise starts to rattle the room. Then out they come, four leather-clad nymphs, flanked and framed by ten-foot flames. Air horns. Lasers. High-definition everything. A blast of heat and light as two massive, inflatable playing cards — an ace of spades, a queen of hearts, blackjack! — drop to the stage like sails. The song is "Fire," a synapse-slapping debut single from way back in 2009, the one that gave South Korea reason to memorize the names and faces of CL, Minzy, Dara, and Bom, the women of 2NE1.

After stepping aside briefly for a cameo by Bigbang (K-pop boy-band royalty), the foursome plow through "Can't Nobody" and "Go Away," two more early numbers for all the diehards (they call themselves Blackjacks). Though 2NE1 are the young guns on the bill, they seem like frontrunners in a race to find serious footing in the American market. They're of a rare species: the "girl group" with growl, a versatile, outwardly independent outfit just as comfortable breaking hearts as they are playing the heartbroken.

Yet even to a casual observer of turn-of-the-century American teen pop, the algorithms at work tonight are crystalline: Bigbang borrow from 'N Sync and Se7en channels Michael Jackson by way of Usher; 2NE1 bow at the altar of TLC and Gummy to Mariah Carey; Jinu, one half of pioneering Korean hip-hop duo Jinusean, lets loose with a "J-J-J-Jinusean" in the key of G-Unit between each of their songs.

A trainee goes through the regimen for two years. I'm not sure other countries or labels have that patience. Every time they perform a song, it's got to be perfect. — Yvonne Yuen, VP of international marketing for Universal Music

Tonight belongs to the guys in Bigbang. Since frontman G-Dragon went into hiding in 2011 after the rare K-pop scandal (he tested positive for smoking marijuana but was never charged), this performance marks a triumphant onstage reunion for the group. They seem up for it; you can feel it in their gravitational pull. They move more like moussed-up panthers or professional athletes than pop stars. When G-Dragon's childhood friend and fellow rapper-singer T.O.P approaches, it's as if the city's been tipped on its side for 30 seconds.

Your once laconic, germaphobic neighbors hurtle and squeeze into one corner of the section like a pile of giggling carp along a catwalk, mouths agape, eyes wild, hearts doing weird things inside their chests. T.O.P swivels and smirks, as if to puckishly half-acknowledge the frisson at his feet. He probably took a class on this. A beat drops, your eyes water. A hook arrives, you laugh to breathe. Kids are running in place, clutching their faces, screaming in so many different frequencies that the sum resembles what it must sound like if someone could roll down the window on a 737 six miles up.

With an hour left, some of them are starting to collapse from exhaustion, their friends catching and carrying them out with such calm it feels like just another part of the ritual. Not long before Bigbang begin their encore, a wavy-haired, thirtysomething American woman grabs my arm. "How do I get out of here?" she shouts. "How do I get out of here?!"

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