At slightly over 17 minutes, it occupies the entire second side of the album. The lyrics, a love song from the biblical Adam to his mate Eve, are simple and are heard only at the beginning and the end. The middle of the song features a two-and-a-half-minute Ron Bushy drum solo.
"In-A-Gadda-Da-Vida" was Iron Butterfly's only song to reach the top 40, reaching number 30, while the album itself reached number four on the album chart and sold over a million copies. An 8-minute-20-second edit of the song was included in the soundtrack to the 1986 film Manhunter. In 2009, it was named the 24th-greatest hard rock song of all time by VH1. It is also often regarded as an influence on heavy metal music and one of the firsts of the genre.
Though it was not recorded until their second album, "In-A-Gadda-Da-Vida" was written during Iron Butterfly's early days. According to drummer Ron Bushy, organist-vocalist Doug Ingle wrote the song one evening while drinking an entire gallon of Red Mountain wine. When the inebriated Ingle then played the song for Bushy, who wrote down the lyrics for him, he was slurring his words so badly that what was supposed to be "in the Garden of Eden" was interpreted by Bushy as "In-A-Gadda-Da-Vida".
Even though nearly all of Iron Butterfly's songs were quite structured, the idea of turning the minute-and-a-half-long ballad into an extended jam emerged very early; Jeff Beck claims that when he saw Iron Butterfly perform at the Galaxy Club on Sunset Boulevard in Los Angeles in April 1967, half a year before the band recorded their first album, their entire second set consisted of a 35-minute-long version of "In-A-Gadda-Da-Vida".
Portions of the song are featured in a 1995 episode of The Simpsons, "Bart Sells His Soul", in which Bart Simpson tricks Reverend Lovejoy's church into singing the song as an opening hymn by handing out sheet music titled "In the Garden of Eden" by "I. Ron Butterfly". Lovejoy describes the hymn as "sound[ing] like rock and/or roll". The church organist, an elderly woman, collapses after playing for the entire seventeen minutes.