Neel's death was confirmed on his official Facebook account, with the post noting he died "from a massive heart failure."
"Aside from being an amazing musician and singer, Johnny was one of the funniest people on the planet — a true character," Haynes wrote on social media. "'Johnny Neel stories,' as we refer to them in our little chunk of the music world, are legendary."
Neel joined the Allman Brothers Band in 1989 ahead of their second reunion tour. He played keyboards in the group and also appeared on their 1990 album Seven Turns, co-writing four songs on the record, including the single "Good Clean Fun."