Think of the work required to make just one Justin Bieber. The production, the management, the vocal training, the choreography, the swagger coaching — all that effort to create one teen-pop star in a country that’s still starving for them. South Korea has no such drought, thanks to several companies that specialize in manufacturing a steady stream of teenage idols, in groups of various configurations. One of the longest-running of these companies is SM Entertainment, which on Sunday night hosted SM Town Live, a sold-out showcase at Madison Square Garden for several of its acts, any one of which any American reality-TV talent show or major-label A&R department worth its salt would be thrilled to have discovered.

American teen-pop at its peak has never been this productive. K-pop — short for Korean pop — is an environment of relentless newness, both in participants and in style; even its veteran acts are still relatively young, and they make young music. Still, there were subtle differences among the veterans, like BoA and TVXQ, and the newer-minted acts like Super Junior, Girls’ Generation and SHINee.

Members of the younger set are less concerned with boundaries, drawing from the spectrum of pop of the last decade in their music: post-Timbaland hip-hop rumbles, trance-influenced thump, dance music driven by arena-rock guitars, straightforward balladry.

Of these groups, the relative newcomer SHINee was the most ambitious. From the looks of it, the group’s men are powered by brightly colored leather, Dr. Martens boots and hair mousse. Their music, especially “Replay,” “Ring Ding Dong” and “Juliette,” felt the riskiest, even if it only slightly tweaked that polyglot K-pop formula; these vocalists were among the night’s strongest.