"Calling to the Night" is the vocal theme for Metal Gear Solid: Portable Ops and Metal Gear Solid: Portable Ops Plus. The song was composed by Akihiro Honda, arranged by Norihiko Hibino and Akihiro Honda, performed by Natasha Farrow, and (its lyrics) written by Nobuko Toda. The song was first featured as an instrumental track in Metal Gear Solid 2: Sons of Liberty, during the cutscene in which Emma Emmerich and Raiden take the ladder down to the oil fence between struts of the Big Shell.