Phil Lesh, legendary bassist and founding member of The Grateful Dead, died on Friday at the age of 84, according to a post on his Instagram account.

Lesh “passed away peacefully on Friday morning” while “surrounded by his family and full of love,” the post said. His cause of death is unclear at this time.

Lesh formed The Grateful Dead in 1965 with Jerry Garcia, Ron “Pigpen” McKernan, Bob Weir and Bill Kreutzmann in Palo Alto, California. He was a member of the band – which had a huge following and was known for blending elements of rock, blues, jazz, folk, country and bluegrass – for its entire three-decade existence.

Lesh’s contribution to The Grateful Dead came primarily as bassist, but he also sang harmony and lead vocals, while co-writing some of the band’s biggest hits, including “St. Stephen” and “Dark Star.” He also has songwriting credits on “Cumberland Blues,” “Truckin’” and “Box of Rain.”

Known for his wide range of skills on the bass, and his talent for using atypical chord structures and timestamps, Lesh was never afraid to make sonic experiments with his fellow bandmates.

“I’m one of those guys who’s always open,” he said Relix in 2010. “Look, music is infinite. There’s an infinite number of ways to do it, an infinite number of melodies that can have a one-four-five progression, it’s absolutely infinite, no floors, no ceiling.

Lesh was born on March 15, 1940 in Berkeley, California. He played viola and trumpet growing up and eventually found an interest in composing. He attended UC-Berkeley, but dropped out during his first semester to pursue a career in music.

In 1994, Lesh and The Grateful Dead were inducted into the Rock & Roll Hall of Fame before disbanding in 1995 following Garcia’s death. Many consider The Grateful Dead to be one of the most influential rock bands in history.

“Jerry was the lynchpin,” Lesh told the newspaper Rolling stone after death. “We were the spokespersons. And the music was the tread on the steering wheel.”

After the breakup, Lesh played in several offshoot bands, including the Other Ones – with Weir, Kreutzmann and Mickey Hart, drummer for The Grateful Dead – the Dead and Further and Phil Lesh and Friends. He stopped touring in 2014.

In 2015, Lesh, Wier, Hart and Kreutzmann reunited for a five-concert series called “Fare Thee Well: Celebrating 50 Years of the Grateful Dead.”

Lesh received a liver transplant in 1998 due to hepatitis C, which began his advocacy for organ donations. He also survived prostate cancer in 2006 and announced he was diagnosed with bladder cancer in 2015.

In the fall of 2015, Hart, Kreutzmann and Weir teamed up with guitarist John Mayer, keyboardist Jeff Chimenti and bassist Oteil Burbridge to tour under the band name “Dead & Company” until 2023.