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

Reed died in Southampton, N.Y., of an ailment related to his recent liver transplant, according to his literary agent, Andrew Wylie, who added that Reed had been in frail health for months. Reed shared a home in Southampton with his wife and fellow musician, Laurie Anderson, whom he married in 2008.

Reed never approached the commercial success of such superstars as the Beatles and Bob Dylan, but no songwriter to emerge after 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, Reed’s early patron.

Indie rock essentially begins in the 1960s with Reed and the Velvets; the punk, New Wave and alternative rock movements of the 1970s, ’80s and ’90s were all indebted to 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!”

Reed’s trademarks were a monotone of surprising emotional range and power; slashing, grinding guitar; and lyrics that were complex, yet conversational, designed to make you feel as if Reed were seated next to you. Known for his cold stare and gaunt features, he was a cynic and a seeker who seemed to embody downtown Manhattan culture of the 1960s and ’70s and was as essential a New York artist as Martin Scorsese or Woody Allen.

Reed’s 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 Reed’s songs explorations of right and wrong and quests for transcendence.

He had one top 20 hit, “Walk On the Wild Side,” and many other songs that became standards among his admirers, from “Heroin” and “Sweet Jane” to “Pale Blue Eyes” and “All Tomorrow’s Parties.” Raised on doo-wop and Carl Perkins, Delmore Schwartz and the Beats, Reed helped shape the punk ethos of raw power, the alternative rock ethos of irony and droning music and the art-rock embrace of experimentation, whether the dual readings of Beat-influenced verse for “Murder Mystery,” or, like a passage out of Burroughs’ “Naked Lunch,” the orgy of guns, drugs and oral sex on the Velvets’ 15-minute “Sister Ray.”

An outlaw in his early years, Reed 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 and their landmark debut album, “The Velvet Underground & Nico,” was added to the Library of Congress’ registry in 2006.

Reed called one song “Growing Up in Public” and his career was an ongoing exhibit of how any subject could be set to rock music — the death of a parent (“Standing On Ceremony), AIDS (“The Halloween Parade”), some favorite movies and plays (“Doin’ the Things That We Want To”), racism (“I Want to be Black”), the electroshock therapy he received as a teen (“Kill Your Sons”).

Reviewing Reed’s 1989 topical album “New York,” Village Voice critic Robert Christgau wrote that “the pleasure of the lyrics is mostly tone and delivery — plus the impulse they validate, their affirmation that you can write songs about this stuff. Protesting, elegizing, carping, waxing sarcastic, forcing jokes, stating facts, garbling what he just read in the Times, free-associating to doomsday, Lou carries on a New York conversation — all that’s missing is a disquisition on real estate.”