Guitarist and Southern rock legend Col. Bruce Hampton collapsed onstage Monday during a performance at his 70th birthday celebration in Atlanta and died later that night.

Hampton collapsed during a lengthy version of “Turn on Your Lovelight” at Hampton 70, a birthday concert featuring members of Phish, Widespread Panic, Leftover Salmon and others at the Fox Theater. John Popper, Warren Haynes, Derek Trucks, Susan Tedeschi and Chuck Leavell were among the musicians performing when he suffered a heart attack. He died at a local hospital.

Hampton, born Gustav Berglund III, first recorded with Frank Zappa and the Mothers of Invention in the 1960s before forming the Hampton Grease Band. Their Zappa/Beefheart-inspired take on blues rock attracted Capricorn Records founder Phil Walden to manage the act. They released a single album on Columbia, Music to Eat, which was long considered the second-poorest selling album in the label’s history.

Hampton left the band in 1973 to re-join Zappa, eventually recording his solo debut in 1978. He had two bands in the 1980s, New Ice Age and Late Bronze Age, but it wasn’t until the 1990s that he found his footing with the heavy-on-improvisation Aquarium Rescue Unit.

That band, which recorded for Capricorn, was an early influence on acts that would come to define the jam band scene; he also helped found the H.O.R.D.E. Tour that featured acts such as Blues Traveler, Black Crowes and the Allman Brothers Band. Its members included guitarist Jimmy Herring, future Allman Brothers bassist Oteil Burbridge and drummer Jeff Sipe, who works with Phil Lesh and Bela Fleck. The group split up in 1993 and reunited in 2015 for a 13-date tour.

After Aquarium Rescue Unit, Hampton went on to form The Fiji Mariners, The Quark Alliance and Col. Bruce Hampton and The Pharaoh Gummitt.

Hampton was leading a weekly residency at the Vista Room in Atlanta that was scheduled to run through May.

R.E.M.’s Mike Mills, the Tedeschi Trucks Band and el-p were among the acts expressing condolences on Twitter.