Iron Butterfly made its New York City debut at the Fillmore East in the spring of 1968, recording all four shows from April 26 and 27. The tapes reveal the Los Angeles quartet – singer/organist Doug Ingle, bassist Lee Dorman, guitarist Erik Brann (just 17 at the time) and drummer Ron Bushy – on the verge of its defining success, mixing tracks from its first album Heavy, with songs that would appear two months later on the band’s multi-platinum magnum opus, In-A-Gadda-Da-Vida.
The well-defined sound heard on these previously unreleased recordings is the result of the quality of the original tapes and the meticulous restoration used to prepare them for this project. Original recording engineer Lee Osborne recorded all the shows using a ½” four-track recorder running at 15 ips. Unfortunately, audio signal issues made the first two songs from the second set on April 26 unusable. 
What remains, as veteran music journalist David Fricke writes in set’s the liner notes, “is the sound of hard-rock immortality in the making…” For the performances, Iron Butterfly drew material primarily from the just-released album Heavy, playing the tough yet nimble “Unconscious Power” in the early show both nights, and closing all four sets with the potent one-two punch of “So-Lo” and “Iron Butterfly Theme.” 
The band also used the Fillmore concerts to showcase three songs from what would become Iron Butterfly’s second album, including “Are You Happy,” “My Mirage” and its title track, “In-A-Gadda-Da-Vida,” which the group deployed to great effect in the second set both nights. 
Fricke writes: “[T]hese recordings, from that spring weekend in 1968, catch Iron Butterfly – and “In-A-Gadda-Da-Vida” – at a transformative point and ferocious pitch: 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.”