https://en.wikipedia.org/wiki/Iron_Butterfly
Classic lineup of Iron Butterfly in 1969: from left to right Doug Ingle, Ron Bushy, Lee Dorman, Erik Brann... Erik Brann left the band after a final show in San Diego on December 13, 1969. Brann was frustrated with the band’s unwillingness to move towards a harder rock sound. He was replaced in the line-up by two new musicians: guitarist/vocalist Mike Pinera (whose Blues Image had opened for Iron Butterfly’s Vida tour) and guitarist Larry Reinhardt (from the Allman Brothers Band forerunner Second Coming)... Dorman and Reinhardt subsequently founded Captain Beyond.
Great tune, man. Never heard it before but I can vouch for its legitimacy to the early seventies.