f(x) (에프엑스) is a south korea-based girl group formed by s.m. entertainment in 2009. since their debut, f(x) has released four full-length albums, two extended plays, and one repackaged album. f(x) has been recognised for their experimental style and eclectic, electropop-based sound. they are one of the few recognized k-pop groups internationally, becoming the first k-pop act to perform at sxsw. the group is currently composed of four members: victoria, luna, amber, and krystal. sulli was a part of the original 5 member line up, but departed from the group in 2015 shortly after ‘red light’ promotions in order to pursue her acting career. their latest comeback, the 4th full album ‘4 walls’, was subject to favorable reviews from music critics. jeff benjamin from billboard shared that despite the fact that the album was “arguably worse” than f(x)’s previous albums pink tape (2013) and red light (2014), it allowed the other members to showcase their vocal abilities more following the departure of sulli. he praised it as a “rarity in k-pop to do once” by “finding the right sonicscapes” and appreciated the “house and trendy dance” production. benjamin subsequently named ‘4 walls’ the second best k-pop album of 2015.