Many have attempted to blend R&B and hip-hop with K-pop, but no girl groups have done it with the whip-smart style of this foursome. After six years together, Jun Hyoseong, Jung Hana, Song Jieun and Han Sunhwa are still going strong. While other K-pop groups embrace a plastic sound, Secret goes for a vintage feel, complete with fat horns and disco basslines. If Amy Winehouse and Beyoncé moved to Seoul to start a girl group, this is what it would sound like. And like Destiny's Child at the peak of their powers, this four-woman partnership just keeps getting stronger.