f(x) - 어렵고도 쉬운 (Difficult But Easy) (Sung by LUNA & Krystal) (OST Invincible Lee Pyung Kang Part.3)
f(x) - 첫 사랑니 (Rum Pum Pum Pum)
f(x) - 미행 (그림자: Shadow)
f(x) - Pretty Girl
f(x) - Kick
f(x) - 시그널 (Signal)
f(x) - Step
f(x) - Goodbye Summer (Sung by Amber Liu & LUNA & Krystal) (Feat. D.O. of EXO)
f(x) - Airplane
f(x) - Toy