John Cale, who co-founded the Velvet Underground but had a sometimes fractious relationship with his former bandmate, released a statement on his Facebook page: "The world has lost a fine songwriter and poetI've lost my 'school-yard buddy'," he said.
Cale and Reed put aside their differences to release a tribute album to Warhol in 1990 called 'Songs for Drella', which led to a handful of reunion performances of the Velvet Underground's original lineup in the early 1990s.
Musician Iggy Pop's official Twitter account called the news "devastating," while musician Kim Gordon of Sonic Youth tweeted: "So sorry to hear of Lou Reed's passing this is a huge shock!"
An admitted hard drinker and drug user for many years, Reed underwent a liver transplant earlier this year at the Cleveland Mayo Clinic, his wife, Laurie Anderson, told The Times of London after he had canceled five California April concert dates.
"I am a triumph of modern medicine," Reed posted on his website on June 1, 2013, without directly acknowledging the transplant. "I look forward to being on stage performing, and writing more songs to connect with your hearts and spirits and the universe well into the future."
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Lyrics that shocked
Reed shocked with lyrics that chronicled sex and drugs, notably in "Heroin" in which Reed declares, "It's my wife, and it's my life," and in Reed's only Top 10 single, "Walk on the Wild Side," one of several songs referencing transsexuals.
"Sister Ray" —a 17-minute blast of guitar distortions—combined stories of sailors, oral sex, murder, intravenous drug use and the mysterious title character.
"I never in a million years thought people would be outraged by what I was doing," Reed said in a 1989 interview with Rolling Stone. "You could go to your neighborhood bookstore and get any of that."
One of his signature songs, first performed by the Velvet Underground and later a staple of his solo act, was simply titled "Rock and Roll," a semiautobiographical story of how music saved the life of a young fan listening on the radio.
His avant-garde act in a dog collar and eye makeup opened the door for artists such as David Bowie to take androgynous looks into the mainstream.
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It was personified in the landmark live album "Rock 'n' Roll Animal," released in 1974. That record closely followed the studio-record rock opera album "Berlin," which he brought to life again with a 2006 concert that was made into a 2007 film directed by Julian Schnabel.
Later in his career, Reed became an elder statesman of rock, a towering figure in a club with legends such as Bob Dylan and Neil Young.
Reed always placed great importance on song-writing. One of his first jobs out of college was as a staff writer for Pickwick Records. He dedicated the 1966 Velvet Underground song "European Son" to the late poet Delmore Schwartz, under whom he studied at Syracuse University.
Reed was married three times, the latest to recording and performance artist Laurie Anderson in 2008, and in recent years took an intense interest in photography, staging exhibitions of his work.