Gregg Allman, a founding member of the Allman Brothers Band, the incendiary group that inspired and gave shape to both the Southern rock and jam-band movements, died on Saturday at his home in Savannah, Ga. He was 69.

His publicist, Ken Weinstein, said the cause was complications of liver cancer.

The band’s lead singer and keyboardist, Mr. Allman was one of the principal architects of a taut, improvisatory fusion of blues, jazz, country and rock that — streamlined by inheritors like Lynyrd Skynyrd and the Marshall Tucker Band — became the Southern rock of the 1970s.

[ Listen to 10 definitive Gregg Allman songs ]

The group, which originally featured Mr. Allman’s older brother, Duane, on lead and slide guitar, was also a precursor to a generation of popular jam bands, like Widespread Panic and Phish, whose music features labyrinthine instrumental exchanges.

Mr. Allman’s percussive Hammond B-3 organ playing helped anchor the Allman Brothers’ rhythm section and provided a chuffing counterpoint to the often heated musical interplay between his brother and the band’s other lead guitarist, Dickey Betts.