Singer Marty Balin, the co-founder of US psychedelic rock band Jefferson Airplane, has died while being taken to a hospital in Tampa, Florida.
The 76-year-old's cause of death was not disclosed by his family and publicist.
Jefferson Airplane defined the 1960s San Francisco Sound – a mix of blues, folk, rock and jazz, and the musical expression of the emerging hippie lifestyle.
Jefferson Starship, the splinter band formed in 1974 that Balin was also in for a number of years, paid tribute to their former bandmate on Facebook.
It said: "With heavy hearts, we learn today of the passing of Marty Balin.
"He was a true talent and inspiration to many. We send his family and friends our deepest condolences."
His wife Susan Joy Balin said: "Marty and I shared the deepest of love he often called it Nirvana and it was. But really, we were all touched by his love. His presence will be within my entire being forever."
Jefferson Airplane was the breakout act among such San Francisco-based artists as the Grateful Dead and Janis Joplin.
Many of them played early shows at the Matrix, a ballroom that Balin helped run and where Jefferson Airplane was the house band.
In 1965, Balin teamed up with guitarist Paul Kantner in San Francisco to form the group and they launched their debut album Jefferson Airplane Takes Off a year later.
The band was best known for their hits sung by vocalist Grace Slick, including Somebody to Love and White Rabbit.
Jefferson Airplane played the Woodstock music festival in 1969 and was inducted into the Rock and Roll Hall of Fame in 1996.
Balin also wrote songs like Volunteers and Today for the band, as well as contributing to hits for Jefferson Starship in the mid-1970s, including Runaway and Miracles.
The band went through various line-ups, and Balin left Jefferson Starship in 2008 to focus on a solo career during which he had success with Hearts and Atlanta Lady.
Balin admitted he was jealous of Slick, who joined Jefferson Airplane in the autumn of 1966 soon before it recorded its landmark second album, Surrealistic Pillow.
He told Relix magazine in 1993: "Every time I did something, it was always Grace Slick and Jefferson Airplane and Grace Slick and the Starship.
"Even if it was my voice. I've even done songs of mine on my own and people come up to me and say, 'I'm surprised you do that song. I always thought it was Grace's.'
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"For a while that hurt my feelings, but there's nothing I can do about it."
Balin underwent heart surgery in 2016 and last month he filed a civil lawsuit for malpractice against a New York City hospital, saying he left the hospital with a damaged tongue and vocal chords.