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Lou Reed, who founded the influential Velvet Underground and went on to a solo career that spanned decades, died Sunday in Southampton, N.Y., his literary agent confirmed to NBC News. He was 71.

"I regret to confirm that Lou Reed has died from complications following a liver transplant," his agent Andrew Wylie wrote in an email. Rolling Stone was the first to report the news.

Reed received the transplant in May. Reed's wife, performance artist Laurie Anderson, said at the time, " "It's as serious as it gets. He was dying. You don't get it for fun."

The singer had canceled planned performances at the Coachella Valley Music and Arts Festival in April because of health issues.

"With the Velvet Underground in the late Sixties, Reed fused street-level urgency with elements of European avant-garde music, marrying beauty and noise, while bringing a whole new lyrical honesty to rock & roll poetry," Rolling Stone wrote in a tribute to the singer. "As a restlessly inventive solo artist, from the Seventies into the 2010s, he was chameleonic, thorny and unpredictable, challenging his fans at every turn."

The Velvet Underground, considered the house band of artist Andy Warhol's studio, The Factory, in the 1960s, never reached commercial success in their time, but are reverently cited by many modern musicians.

"If Reed had never made any solo records, his work as the principal lead singer and songwriter for the Velvets would have still ensured his stature as one of the greatest rock visionaries of all time," AllMusic.com writes in Reed's online biography.

The band's 1967 debut album, "The Velvet Underground & Nico," was named the 13th greatest album of all time by Rolling Stone.

In 1986, Reed told TODAY's Rona Elliot that the public perception that the Velvet Underground's music was all about his life was incorrect.

"If it was all autobiographical, I'd be dead a hundred times," he said. "And the other thing is that there's not enough about me that's interesting. ... It's like Clint (Eastwood) playing Dirty Harry. I wanted you to really believe I was like that."

Reed also said he had "great novelist ambitions" for the Velvet Underground's songs, but never felt the lyrics pushed the edge. "If (the music) had been a novel, nobody'd think twice about it," he told Elliot. "People just had, and I think still have, a contempt for the form. What we were writing, what I was writing about was no big deal, it's just it hadn't taken place in rock 'n' roll."

After leaving the Velvet Underground, Reed had a 1972 hit with "Walk on the Wild Side." Another 1972 song, "Satellite of Love," was remade in 2004 and reached No. 10 on the U.K. charts. But Reed never chased chart success, and for decades continued to release music, perform, and otherwise influence the musicians who came after him.

After his first marriage ended in divorce, Reed married Anderson in 2008.

Mourning for Reed came fast and furious on social media. Legendary band The Who tweeted, "R.I.P. Lou Reed. Walk on the peaceful side."

And the Seattle-based record label SubPop referenced The Velvet Underground song "Sunday Morning," tweeting, "Sunday Mourning--we're going to miss you, Lou."

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