“The lunatic is in my head,” sang Roger Waters, with harmonies by David Gilmour, on a Pink Floyd song called “Brain Damage.” The song appears on The Dark Side of the Moon—a note-for-note perfect album that has sold more than 45 million copies. Who was that lunatic? Everyone knows Pink Floyd, but does everyone know why they existed?

Syd Barrett, the original Pied Piper, was the face and lysergic brain of Pink Floyd when they released their 1967 studio debut, The Piper at the Gates of Dawn, recorded at Abbey Road in the studio next to the Beatles, who were making Sgt. Pepper. So much of his work is an acid flashback of childhood. “Bike” could have and should have been covered by Pee-wee Herman. Impish, dapper, not quite of this earth, Barrett shone like the sun, but not for long. In Roddy Bogawa and Storm Thorgerson’s new documentary, Have You Got It Yet?—named for an impossible-to-perform Barrett song—we take a deep dive into Barrett’s work and tortured life, the off-kilter whimsy of his songs, his on-and-off engagement to Miss Gala Pinion and the two rings that went with it, and the long years of silence that followed.

In 1972, just seven years after co-founding Pink Floyd, Barrett left the music industry for good.

To tell the tale, we get the surviving members of Pink Floyd, along with every girlfriend and mate still alive, and it is a tribute to National Health that there are so many. Even Pete Townshend and Sir Tom Stoppard are on hand, in awe like the rest of us. As soon as The Piper at the Gates of Dawn was in the Top 10, Barrett was becoming unreliable. We see the band with Dick Clark when Barrett refused to sing and keyboardist Richard Wright had to step in. After Barrett was kicked out of his own band, Waters and Gilmour helped him make two solo albums that are as brilliant as they are demented—outsider art that draws you in. Gilmour tells us that songs such as “Octopus,” “Dominoes,” “Terrapin,” and “Dark Globe” might have been even better than Barrett’s work with the Floyd. Syd was already not quite of this world when he made them, and his descent is palpable.

If Syd had a second act, it was in the Pink Floyd that went on without him and broke very big. Their greatest work is haunted by him—the alienation on The Dark Side of the Moon, the breakdown on The Wall, and, of course, Wish You Were Here, when they wished he was there. It happened that when they were recording a tribute to Barrett, “Shine on You Crazy Diamond,” Barrett, whom they had not seen in years, showed up at the studio, unrecognizable, with a shaved head and eyebrows and an extra hundred pounds. Someone took pictures, and we see them all, evidence that the light had gone out. He was somewhere else, painting sometimes-inspired canvases in Cambridge, and then destroying them.

Pink Floyd in 1967, the year they released their debut studio album, The Piper at the Gates of Dawn.

Pink Floyd and all their success turned bitter and divided, but they had a televised reunion in 2005, and Roger Waters dedicated their performance of “Wish You Were Here” to Syd. At home with his sister, Barrett turned off the telly and died of pancreatic cancer the next year, at 60. He had long gone back to his birth name of Roger and wanted nothing to do with his own legend, but many of us still do. “It was sunny for the first two weeks, and it rained for six years,” said one of his mates. We’ll take it. Shine on.

Have You Got It Yet? is playing in select theaters around the world

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David Yaffe is a professor of humanities at Syracuse University. He writes about music and is the author, most recently, of Reckless Daughter: A Portrait of Joni Mitchell. You can read his Substack here