Lou Reed, the punk poet of rock-and-roll who profoundly influenced generations of musicians as the leader of the Velvet Underground and remained a vital solo performer for decades after, died Sunday at 71.

Mr. Reed died in Southampton, N.Y., of an ailment related to a May liver transplant, according to his literary agent, Andrew Wylie. Mr. Reed shared a home in Southampton with his wife and fellow musician, Laurie Anderson, whom he married in 2008.

No songwriter to emerge after Bob Dylan so radically expanded the territory of rock lyrics. And no band did more than the Velvet Underground to open rock music to the avant-garde — to experimental theater, art, literature and film, to William Burroughs and Kurt Weill, to John Cage and Andy Warhol, Mr. Reed’s early patron.

Indie rock essentially begins in the 1960s with Mr. Reed and the Velvets. The punk, New Wave and alternative rock movements of the 1970s, ’80s and ’90s were all indebted to Mr. Reed, whose songs were covered by R.E.M., Nirvana, Patti Smith and countless others.

“The first Velvet Underground record sold 30,000 copies in the first five years,” Brian Eno, who produced albums by Roxy Music and Talking Heads among others, once said. “I think everyone who bought one of those 30,000 copies started a band!”

Lou Reed performs in 2012 in Berlin. (MATTHIAS BALK/eurpean pressphoto agency)

Before the Velvets, references to drugs and sex in rock lyrics were often brief and indirect, if only to ensure a chance at radio and television play. The Velvets said everything other bands were forbidden to say and some things other bands never imagined. Mr. Reed wrote some of rock’s most explicit lyrics about drugs (“Heroin,” “I’m Waiting for the Man”), sadomasochism (“Venus in Furs”) and prostitution (“There She Goes Again”). His love songs were less stories of boy-meets-girl, than ambiguous studies of the heart.

His trademarks were a monotone of surprising emotional range and power; slashing, grinding guitar; and complex, yet conversational lyrics designed to make you feel as if Mr. Reed were seated next to you.

Known for his cold stare and gaunt features, he seemed to embody downtown Manhattan culture of the 1960s and ’70s — as essential a New York artist as Martin Scorsese or Woody Allen. His New York was a jaded city of drag queens, drug addicts and violence, but it was also as wondrous as any Allen comedy, with so many of Mr. Reed’s songs being explorations of right and wrong and quests for transcendence.

He had one top 20 hit, “Walk On the Wild Side,” and many other songs became standards among his admirers, including “Heroin,” “Sweet Jane,” “Pale Blue Eyes” and “All Tomorrow’s Parties.”

An outlaw in his early years, he would eventually perform at the White House, have his writing published in the New Yorker, be featured by PBS in an “American Masters” documentary and win a Grammy in 1999 for Best Long Form Music Video. The Velvet Underground was inducted into the Rock and Roll of Fame in 1996.

Lewis Allan “Lou” Reed was born in Brooklyn on March 2, 1942. His father was an accountant. Mr. Reed hated school, loved rock, fought with his parents and later attacked them in song for forcing him to undergo electroshock therapy as a supposed “cure” for being bisexual. “Families that live out in the suburbs often make each other cry,” he later wrote.

At Syracuse University, he studied English under poet Delmore Schwartz. He later worked in New York City as a house songwriter at the low-budget Pickwick Records. Fellow studio musicians included a Welsh-born viola player, John Cale, with whom Reed soon performed in such makeshift groups as the Warlocks and the Primitives.

They were soon joined by guitarist-bassist Sterling Morrison and drummer Maureen Tucker, who tapped out simple, hypnotic rhythms and played standing up. The name Velvet Underground came from a Michael Leigh book about sexual paraphilia. They rehearsed at Warhol’s “Factory,” a meeting ground of art, music, orgies, drug parties and screen tests for films that ended up being projected onto the band while it performed, part of what Warhol called the “Floating Plastic Inevitable.”

“Warhol was the great catalyst,” Mr. Reed told BOMB magazine in 1998. “It all revolved around him. It all happened very much because of him. He was like a swirl, and these things would come into being: Lo and behold multimedia.”

At Warhol’s suggestion, they performed with the sultry German-born Nico, a “chanteuse” who sang lead on a handful of songs from their debut album. “The Velvet Underground & Nico” featured a now-iconic Warhol drawing of a (peelable) banana on the cover and proved an uncanny musical extension of Warhol’s blank-faced aura.

On the album’s song “Heroin,” Cale’s viola screeched and jumped behind Mr. Reed’s obliterating junkie’s journey, with his sacred vow, “Herrrrrr-o-in, it’s my wife, and it’s my life,” and his cry into the void, “And I guess that I just don’t know.”

Mr. Reed made three more albums with the Velvet Underground before leaving in 1970. Cale was pushed out by Mr. Reed in 1968 (they had a long history of animosity) and was replaced by Doug Yule. Their sound turned more accessible, and the final album with Mr. Reed, “Loaded,” included two upbeat musical anthems, “Rock and Roll” and “Sweet Jane.”

His albums in the 1970s were alternately praised as daring experiments or mocked as embarrassing failures, whether the ambitious song suite “Berlin” or the wholly experimental “Metal Machine Music,” an hour of electronic feedback. But in the 1980s, he kicked drugs and released a series of acclaimed albums, including “The Blue Mask,” ‘’Legendary Hearts” and “New Sensations.”

He played some reunion shows with the Velvet Underground and in 1990 teamed with Cale for “Drella,” a spare tribute to Warhol. He continued to test new ground, whether a 2002 concept album about Edgar Allan Poe, “The Raven,” or a 2011 collaboration with Metallica, “Lulu.”

Survivors include Anderson. A previous marriage to Sylvia Morales ended in divorce.

— Associated Press