On May 11th, stars performed at the congratulatory music concert for KBS's "INPUT 2011 Seoul". The conference is a four-day long event that brings together representatives from around the world for discussions ranging from public television and the 21st century, to 3D-TV and the future of broadcast television. The concert was broadcasted live on the same day, and boasted a line-up of Insooni, TVXQ, SNSD, 4minute, CNBLUE, Kim Tae Woo, Lim Tae Kyung, Song Sohee and many others. Check out some of the performances below! -- < TVXQ - "Keep Your Head Down" > < TVXQ - "Before U Go" > -- < SNSD - "Hoot" > -- < CNBLUE - "Intuition" > -- < 4minute - "Mirror Mirror" >