Paul Kantner, who helped pioneer psychedelic rock as the guitarist and founder of Jefferson Airplane and its splinter group Jefferson Starship, has died of multiple organ failure and septic shock. He was 74.

SF Gate reports that he had suffered a heart attack earlier in the week. He'd endured numerous health problems in recent years, including a previous heart attack in March 2015.

Born in San Francisco on March 17, 1941, Kantner had been a folksinger in the Bay Area when he met another folike, Marty Balin, in 1965. Over the next couple of years, they recruited guitarist Jorma Kaukonen, bassist Jack Casady, drummer Skip Spence and vocalist Signe Anderson. After releasing their 1966 debut, Spence and Anderson left and were replaced by, respectively, Spencer Dryden and Grace Slick.

The first album with the new lineup, Surrealistic Pillow, was one of the original albums of the growing psychedelic movement, hitting stores four months before the Beatles released Sgt. Pepper's Lonely Hearts Club Band. It spawned Top 10 singles in "Somebody to Love" and "White Rabbit." They performed at both Woodstock and Altamont, the latter of which saw Balin knocked unconscious by a Hells Angel during their set. Kantner sarcastically thanked the motorcycle gang for their action.

But by 1970, after five albums, the band began to come apart. Kantner and Slick, who by now had become a couple, brought together a handful of their fellow San Franciscans and released an album called Blows Against the Empire. The concept album, about humans leaving Earth for outer space, was credited to Paul Kantner and Jefferson Starship, and the Airplane officially split up in 1972.

After a couple more records in this loose all-star format, Kantner, Slick settled on a lineup for the band, and brought Balin back. Jefferson Starship had a poppier edge than its predecessor. Balin's "Miracles," a No. 3 hit in 1975, pushed Red Octopus into the top slot on Billboard's album chart. But after 1978's Earth, which had two more hits in "Count on Me" and "Jane," the internal fighting returned, and Balin and Slick, whose relationship with Kantner ended in 1975, left. Kantner kept Jefferson Starship alive through various incarnations until 1984, when Starship was formed.

He revived Jefferson Starship in 1992, and they remained a viable touring act. Jefferson Airplane were inducted into the Rock and Roll Hall of Fame in 1996.

Kantner is survived by China Kantner, his daughter with Slick, and two sons, Gareth and Alexander.