Tributes have poured in for US musician Phil Everly of the Everly Brothers, who has died aged 74 in California.
His wife Patti told the Los Angeles Times that he suffered complications from lung disease.
Ms Everly said: "We are absolutely heartbroken," and blamed his illness on a lifetime of cigarette smoking. "He fought long and hard," she added.
His son, Jason, said he had been in hospital in Burbank, Los Angeles, for a fortnight before he died. His last public performance was in 2011.
Phil, who took the high notes, and his brother Don were one of the most influential acts of the 1950s and early 1960s.
Known for their distinctive harmonies, they helped define rock and roll with hits including Wake Up Little Susie, Cathy's Clown, Bye Bye Love and All I Have To Do Is Dream.
Their music influenced many rock, country and folk singers, including the Beatles, Simon and Garfunkel and the Byrds.
The Everly Brothers' career spanned five decades. They broke up acrimoniously on stage in 1973 but got back together at a reunion concert at London's Royal Albert Hall 10 years later.
In 1986 they were among the first acts to be inducted into the Rock and Roll Hall of Fame.
Tributes flooded in for Phil, recognising his lasting legacy on the music industry.
US guitarist and friend Duane Eddy, who produced Phil's first solo album after the split with his brother, described his death as "a huge blow".
He told BBC Radio 5 live: "It was the most beautiful sound you'll ever hear I think, of two voices.
"They were like two great singers that came together who happened to be brothers and had that same sibling quality. It just made for a beautiful sound."
Queen guitarist Brian May said he had lost "a huge piece" of his youth and described the brothers as "heroes".
In a post on his website brianmay.com, he wrote: "I could probably write a book on the music of the fabulous Everly Brothers, but you'll find echoes of their influence in a lot of our old Queen songs, and perhaps that is the best tribute."
He added: "I never met them. Wish I had. But they will always be my heroes. I don't think they will know who I am, but my heartfelt condolences to Phil's wife, his family and friends, and of course to Don. I can't imagine how that must be. So hard, So sad.
"RIP Phil Everly ... you were magic. I have tears in my eyes."
English guitarist Albert Lee, who was the musical director for the brothers' reunion concert and performed with them for over two decades, said they had a unique sound.
"There was nothing like it. It was a combination of their country upbringing and when they became teenagers they fell in love with rock and roll," he told BBC News. "They sounded like no one else."