Almost two years after K-pop first giddily barged into America's imagination, the genre hasn't sustained a post-"Gangnam Style" wave, but the Seoul machine keeps humming. Female foursome 2NE1, buoyed by a cameo on The Bachelor, moved more units of their album in its first week of release than any previous Korean act. That was about it for sales records, but the album itself was no stiff; in fact, it's a canny downshift from the wigged-out "I Am the Best" maximalist mash-ups of the past. "Happy" is a sunny, strummy jaunt with no manic gimmicks and the ballad "Good to You" soars and sweet-talks likably. But Crush's centerpiece is "MTBD," which spotlights group member CL on a bratty squirt of EDM-hip-pop with a bubblegum trap groove. C.A.