In 2011, he formed a project group with label mate Jungmo of TRAX called M&D (meaning "Midnight and Dawn" or "Miari and Dangae-dong", after the members' hometowns). They released their debut single, "Close Ur Mouth". Heechul wrote the lyrics and directed the music video for the song, while Jungmo produced and performed the instrumental. Their first live performance was at Mnet’s summer awards ceremony 20’s Choice on July 7.