Gregg Allman has died at the age of 69, after a battle with liver cancer.
Elton offered his thoughts on Instagram, also acknowledging last week's terror attack at Manchester Arena.
''After the most tragic week for music, there is more sad news. Another great musician has left us. Gregg Allman was revered by musicians everywhere. A kind and gentle soul. Much love to his family and friends.''
Warren Haynes, longtime guitarist with the Allman Brothers Band, said:
"I am truly honoured to have been fortunate enough to have written many songs with him and equally honoured to have traveled the world with him while making the best music the world has ever known. I will never, ever take that for granted. And on top of all that - he was my dear friend.''
Cher, who was once married to the performer, tweeted a photo of the pair, and wrote that ''words are impossible.'
Charlie Daniels said that he couldn't believe such a ''magnificent voice is stilled forever.''
Apple's Tim Cook weighed in as well, posting on Twitter: ''Heartbroken at the passing of Gregg Allman. I grew up listening to your soulful voice & will never forget you. RIP midnight rider.''