Australian entertainer Jon English was thought to be doing well just hours before his death, according to his long-term friend, performer Simon Gallaher.
The English-born rock star died on Wednesday night following a small operation for an aortic aneurysm.
A statement released by the 66-year-old's music label, Ambition Music Group, confirmed his death.
"It is with great sadness that we commemorate the passing of Jon English," the statement said on Thursday.
"Jon died peacefully last night, aged 66. The cause of death was post-operative complications."
He was surrounded by his four children, Jessamin, Josephine, Jonnie and Julian, his wife Carmen, his sister Janet, his brother Jeremy, his nephews Jay and Jasper Collie, his grandson Jzawo and other close family members.
English, known for his breakthrough stage role in Jesus Christ Superstar, was due to tour Australia from May starting in Perth, but was forced to cancel several shows earlier in the week because of "unexpected ill health".
He was hospitalised for broken ribs when the aneurysm was discovered.
"They happened just to stumble across this," Gallaher told AAP.
"He was in Adelaide and I think he just fell over and hurt himself that way.
"I was chatting to him in the hospital and he was just there under observation, he was perfectly well in himself although this problem was there."
Gallaher and English starred in Pirates of Penzance together for numerous performances, beginning in the 1980s.
The pair had plans to renew their 30-year onstage partnership later this year in a production of Monty Python's Spamalot.
"He was going to be King Arthur," Gallaher said.
"We did it last year in Brisbane and it was very successful. So we were going to go on tour with that later this year."
Gallaher heard about English's death from the star's present partner Coralea Cameron.
"Jon's partner Coralea sent me a text in the middle of the night, which I ignored. So it wasn't until I woke up that suddenly the world had gone mad," he said.
Gallaher said Cameron had been updating him on English's progress, and that all was well until just hours before his death.
"We'd been in touch a lot and it was only yesterday afternoon that she texted me and she said `Jon's out of surgery and all is well, fingers crossed'," he said.
"That would have only have been 5 o'clock.
"And then at 3.20 this morning she writes to me: `It's with very heavy heart that I send this message to you at this early hour, in the late hours of yesterday evening, Jon passed away due to the complications from his surgery for an aortic aneurysm'."
The singer was due to tour Australia from May starting in Perth, but was forced to cancel several shows earlier in the week due to "unexpected ill health".
"Jon is currently hospitalised and waiting to undergo a small operation, but is expected to make a full recovery over the coming weeks," said a post on his official Facebook page last week.
English won the 1979 Logie Award for Best New Talent in Australia for his role in TV mini-series Against the Wind.
He also won four ARIA awards throughout his career - for his album Turn the Page, his musical Paris and Pirates of Penzance.
The Hollywood Seven singer was set to perform in Orange in NSW's central west in April before touring Australia as part of the Rock Show Oz Edition, which was to kick off in Perth in May.
"We've lost a giant of the industry," Gallaher said.
