Southern rock icon Gregg Allman died at age 69 on Saturday, leaving the music world without one of its central pioneers. The singer-songwriter was integral to the shaping of modern music, so naturally, many musicians are currently mourning his passing.

The Allman Brothers Band confirmed the news they had lost a member on Twitter, saying, “It is with deep sadness we announce that Gregg Allman … passed away peacefully at his home.”

Allman’s ex-wife Cher was also one of the first to voice her sorrow on social media, lovingly referring to he as “Gui Gui.”

Fellow music legends like Ringo Starr, Melissa Etheridge, and Peter Frampton also paid their respects to Allman online.

Etheridge even posted a pic of the pair:

Writing to Variety, longtime Tom Petty keyboardist Benmont Tench sent the following thoughts:

“[Gregg Allman] and the Allman Brothers Band set a standard that every band in Florida, as we were coming up, tried in vain to match. A subtle but lovely and deep player, a wonderful songwriter, and — Lord! — that voice. In that era when white musicians were thrilled by and determined to spread the good news of what black musicians had been up to for years and years, he was to me among the truest, most natural, and effortless-sounding of them all. So many followed in his footsteps, and so very few understood what he so clearly did. A well of knowledge, clearly, whether studied or innate. Irreplaceable. 
“Tom knew him far better than I, and in fact has told me many times of seeing Gregg and Duane in their earliest bands, playing dances, and playing ‘Rubber Soul,’ all the way through, I think, immediately after it came out. 
“Where we were smart, or whatever, back then, was that we knew they were their own world, so we rarely tried to emulate them. But man, oh, man, practically everybody else sure did!”

Allman was especially beloved by the country community, as can been seen by Charlie Daniels, Keith Urban, and Travis Tritt’s tributes.

Even non-musicians like Cameron Crowe and Jeanine Pirro honored Allman for his contributions to pop culture.

It is currently unknown what caused the singer’s death. As recently as April 24, reports surfaced claiming Allman was in hospice. However, his manager denied those reports to Variety, which Allman then substantiated in a Facebook post.

Married and divorced six times, Allman is survived by three sons and two daughters, all by different mothers. Four of the children are professional musicians.