The song was written to create the visual of lights turning on at dusk in a city like Tokyo, beginning with "tinkling" opening notes resembling Christmas lights, and a gradually rising and falling synthesizer rhythm throughout the song. After recording "Seibu", the band set it aside, and the piece was forgotten as the sessions progressed. It was almost left off the album, until guitarist The Edge rediscovered the track while looking through the session's discarded songs. Recognizing its potential to become a great song, The Edge brought "Seibu" to Eno's attention, and in early June 1995, Eno listed "Seibu" as a late entry to be considered for the album. As producer, Eno had most of the artistic control during the sessions, limiting U2's creative input on the recordings, which prompted The Edge to ensure extra work was put into arranging the song. He has said that along with "Miss Sarajevo" and "Your Blue Room", "Seibu" was one of only three tracks from the album in which U2 "really dug in [their] heels and did more work on and tried to craft". By early July 1995, the band renamed the song "Seibu/Slug", and Eno noted that the piece started to sound better and described it as a "lovely song". During the final editing of the track, Eno became angry with U2 because they seemed unfocused and he felt he was doing all the work. Bono decided to completely deconstruct the mix of the song. Eno initially disapproved, but was satisfied after hearing the changes. The editing of the track was finalised on 10 July, and The Edge later said he felt his effort to put extra work into the song "paid off". It was released with the title "Slug" on 7 November 1995, as the second track on the Passengers album "Original Soundtracks 1"; out of the fourteen tracks on the album, it is one of six tracks to feature vocals. Details of the song's recording sessions were documented in Eno's 1996 book, "A Year with Swollen Appendices". As the compositions on "Original Soundtracks 1" were written as film soundtrack music, each track is associated with a specific film in the album's liner notes, which were written by Eno. Four of the fourteen tracks are associated with real films, while "Slug" is credited as having been written for a fictional German film of the same name, directed by "Peter von Heineken" (a reference to U2 manager Paul McGuinness).