Twenty or so years ago, Lou Reed — who died Sunday of liver failure at 71 — published a book called “Beyond Thought and Expression: Selected Lyrics” that casts in stark relief the promise and the pretension of thinking about rock lyrics as poetry.

Reed, of course, always considered himself in such terms, tracing a lineage to the story writer and poet Delmore Schwartz, who had been his teacher at Syracuse University, creating with the Velvet Underground (and later, in solo efforts such as “Berlin,” “Street Hassle,” “New York” and “Songs for Drella”) a kind of rock ’n’ roll as operatic Grand Guignol.

It’s no coincidence that the Velvet Underground's early champion was Andy Warhol, who, in January 1966, installed them as the house band for his Exploding Plastic Inevitable. Like Warhol, Reed was an aesthete who worked in popular forms.

“Beyond Thought and Expression” (Reed also used the title for a three-CD career retrospective) highlights the liberation and the limitation of this sort of thinking. On the one hand, why not frame lyrics as poetry? The first step in being an artist is to claim the territory, and Reed was one of the earliest, and most influential, performers to stake out rock ’n’ roll as art.

Some of his lyrics (“I’m going to try / to nullify my life”) remain as resonant as any lines I’ve heard or read, definitive not just for their clarity, their fluidity, but also because they opened up the form to a way of seeing, a way of thinking, it had not encompassed before. Others — I’m thinking about the Velvet Underground’s recordings such as “The Gift” or “The Murder Mystery” — blur the line between song and story, functioning as extended pieces of prose, of narrative, set to chords and a beat.

Still, there’s no way to read “Beyond Thought and Expression” without wanting to hear the music these lyrics signify: the droning guitars, the cymbal brushes, the flat, nasal Brooklynese of Reed’s talk-singing as it slurs around the rhythm of the song.

“One chord is fine. Two chords are pushing it. Three chords and you’re into jazz,” Reed once declared, but while that’s true enough as it goes, it also belies a certain sneaking complexity, an ambition that even his most direct work (“Sweet Jane,” “Vicious,” “Satellite of Love”) embodies at its heart.

This is why Reed, for all his protean abilities as a guitarist, surrounded himself with top-flight players throughout his career: John Cale, Steve Hunter, Robert Quine. Like him, they were visionaries – innovative, brainy musicians who existed in the middle territory between pop culture and the avant-garde.

The same might be said of his songwriting, which relies on a surface accessibility to get at deeper concerns. “Thought of you as my mountain top,” he writes in “Pale Blue Eyes,” “thought of you as my peak / thought of you as everything / I’ve had but couldn’t keep.”

Reed is evoking an illicit relationship, but he’s also reflecting a more expansive sense of longing, the longing inherent in being alive. For this reason, his most beautiful songs are often his most disturbing — “The Gun,” for instance, or the exquisite “The Last Shot,” with its matter-of-fact portrayal of an ex-addict still yearning for the drugs. What makes this remarkable is that it’s utterly unsentimental (“when you quit, you quit / but you always wish you knew it was / your last shot”), aware of the brutality it describes but mourning it anyway.

It is, of course, a loaded game to frame rock ’n’ roll as poetry. Besides Patti Smith — who, after all, has an actual poetic practice — what poets has rock given us? Dylan? Perhaps, although I’m not sure the label does justice to his achievement, which exists outside such categories. Lennon, Neil Young, Nick Cave, Jeff Tweedy? As much as I admire them, to call their songs poetry is to miss the point.

Reed’s insistence on being considered a poet tells us something of his insecurities, of his personality, which could be difficult even at the best of times. But it also tells us something of his aspirations, of the seriousness with which he approached his work. When I heard that he had died, I felt as if I’d lost a friend … or no, not a friend but a teacher, as he felt about Delmore Schwartz.

Simplicity of expression, depth of thought, the phrase goes, but whatever way you put it, Reed taught me that you could write anything, no matter how harsh or brutal, if you could find the proper frame. What else do we say about a songwriter whose most resonant material deals with degradation — not out of prurience or shock value but, rather, the deepest connection, the understanding that all of us (whatever our vices or predilections) feel degraded in some way?

“I have never thought,” Reed once observed, “of music as a challenge — you always figure the audience is at least as smart as you are. You do this because you like it, you think what you’re making is beautiful. And if you think it’s beautiful, maybe they think it’s beautiful.”

That sums up his aesthetic in a nutshell, the vivid power of his songs. Poet, songwriter, singer, guitarist: the labels don’t matter. They never did. “But you know,” he wrote in “Street Hassle,” “people get all emotional and sometimes, man / They don’t act rational / They think they’re on TV.”

There it is again, that intention, pop culture blurring into something deeper, something darker, something that tells us who we are.

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