In April 1968, 'In-A-Gadda-Da-Vida' was more of a tongue twister than one of the most recognizable psychedelic guitar jams ever recorded. Iron Butterfly took the stage at the Fillmore East in New York City looking to change that, and over four shows in two nights the rock quartet set the first paving stones toward a great rock career.

Veteran rock journalist David Fricke calls the double disc 'Fillmore East 1968' compilation, “The sound of hard-rock immortality in the making.” It's the best 22 songs from the early spring performance, captured on a half-inch four-track recorder and meticulously restored to today's standards. The album will be out on Oct. 18.

The majority of the songs are from the Los Angeles band's debut album 'Heavy.' Included are multiple versions of 'So-Lo' and 'Iron Butterfly Theme.' The band also previewed songs from their second album including  'Are You Happy,' 'My Mirage' and the title track, the legendary 'In-A-Gadda-Da-Vida.'

“These recordings, from that spring weekend in 1968, catch Iron Butterfly -- and 'In-A-Gadda-Da-Vida' -- at a transformative point and ferocious pitch," Fricke, who also wrote the liner notes, says. "A great acid-garage band with sharp pop instincts, hardened and tightened by long service on the Sunset Strip, about to establish a lasting definition of heavy rock.”

The band has had multiple lineups since forming in 1966, the four members at the time of this recording were lead singer/organist Doug Ingle, bassist Lee Dorman, guitarist Erik Brann (just 17 at the time) and drummer Ron Bushy.