Doug Ingle, the co-founder of the 1960s rock band Iron Butterfly and the voice behind their iconic hit “In-A-Gadda-Da-Vida,” has died at the age of 78.

His death was announced by his son, Doug Ingle Jr., in a heartfelt social media post on May 24, reported Rolling Stone. He did not provide a cause of death.

“It’s with a heavy heart & great sadness to announce the passing of my Father Doug Ingle. Dad passed away peacefully this evening in the presence of family,” wrote Ingle Jr. “Thank You Dad for being a father, teacher and friend. Cherished loving memories I will carry the rest of my days moving forward in this journey of life. Love you Dad.”

Ingle, who sang and played the organ for Iron Butterfly, was the last surviving member of the band’s classic late-1960s lineup.

Formed in San Diego, Iron Butterfly achieved fame with their 17-minute epic “In-A-Gadda-Da-Vida,” which sold an estimated 30 million copies worldwide.

The title famously originated from a drunken misinterpretation of “In the Garden of Eden” by the late drummer Ron Bushy.

The song left a significant cultural imprint, even making a memorable appearance in a 1995 episode of “The Simpsons,” titled “Bart Sells His Soul.”

It has also been covered by numerous artists, including Slayer and the Residents, and was even featured in films like Michael Mann’s “Manhunter.”

Iron Butterfly would eventually disband in 1971 but reunited several times over the years, with Ingle participating in brief reunions in the late ’70s and ’80s, and a longer stint in the ’90s until his retirement in 1999.