Lou Reed issued one of the most puzzling albums in rock history in 1975

STEVE INSKEEP, HOST:

The story of one of the most head-scratching decisions in the history of rock and roll.

(SOUNDBITE OF SONG, "WALK ON THE WILD SIDE")

LOU REED: (Singing) They said, hey, sugar, take a walk on the wild side.

INSKEEP: That was a big hit for Lou Reed, who made the pop charts in 1973 with "Walk On The Wild Side," after years on the fringes. So he'd made it. And then, just a couple of years later, he tried this new sound.

(SOUNDBITE OF LOU REED SONG, "METAL MACHINE MUSIC, PT. 1")

INSKEEP: Ow. This is called "Metal Machine Music," a bed of pulsating screeches and noise that went on for an hour. That was the album. Fans were repelled. Recently, though, it's inspired a new generation and a new approach. Here's NPR's Phil Harrell.

PHIL HARRELL, BYLINE: "Metal Machine Music" initially sold around 100,000 copies. According to legend, a shocking number of them were returned for refunds.

WILL HERMES: A friend of mine described it as seagulls circling over an expansive radioactive garbage.

HARRELL: That's critic Will Hermes. He recently wrote the book "Lou Reed: The King Of New York."

HERMES: It's basically just electric guitars in open tunings, which when leaned against an amplifier, create loops of feedback. And he layered the recordings. So it's really kind of a symphony of guitar feedback made with multiple instruments.

HARRELL: At the time, fans theorized that Lou Reed was just trying to get out of a bad recording contract by delivering a double album's worth of noise, but he always insisted that it was a genuine work of art, perhaps his greatest. Since then, it's been treated that way by musicians who've studied it as a serious piece of composition.

(SOUNDBITE OF LOU REED SONG, "METAL MACHINE MUSIC, PT. 1")

HARRELL: Is this good?

HERMES: Well, it depends on your definition of good. Good for what? It's...

HARRELL: Driving fugitives out of embassies, I think.

HERMES: As a work of art, it's pretty interesting. You could put it on the background and use it as ambient music. You could sit and attend to it very closely. May work for you, may not.

HARRELL: Other people insist you can't understand the work if you only listen to little snippets. That's the position of Dave Gebroe. He hosts a podcast for music obsessives called "Discograffiti."

DAVE GEBROE: It's kind of like doing a flotation tank for one minute and going, OK, I get it. I'm floating in water. And not letting yourself be uncomfortable before you break through to not knowing any sense of time and space. It's not about the music or the noise itself. It's about the effect that it produces.

HARRELL: Gebroe is behind a new tribute album of sorts. He asked four different artists to record their own interpretations of "Metal Machine Music." Some of the new versions are every bit as loud and aggressive as the original. Others are kind of trippy. Lou Barlow of the band Dinosaur Jr. even added a spoken word component.

GEBROE: It's very much a sonic collage, and he's reading on top of it a particularly torn diary entry and has slowed down his voice.

(SOUNDBITE OF SONG, "METAL MACHINE MUZAK")

LOU BARLOW: (Reading) Bring meaning to action - find words to explain it but somehow elude how out of control and magical it can be.

GEBROE: One of the beautiful things about "Metal Machine Music" is it's completely in the eye of the beholder. Your version of the truth of this record is how you perceive it.

HARRELL: Dave Gebroe named these new interpretations, "Metal Machine Muzak." So if you have an hour sometime, luxuriate in that flotation tank.

Phil Harrell, NPR News. Transcript provided by NPR, Copyright NPR.