Harold Eugene Clark and Ingram Cecil Connor III – who grew up to be Gram Parsons – were both Southern boys, born a few years apart. Parsons was wealthy; Gene Clark was working-class. But both of them picked up guitars early on, moving with the times from rock and roll combos to folk groups before making their way to Los Angeles, where they ended up playing with the same musicians and, occasionally, with each other. Both of them passed through the Byrds: Clark formed the band with Jim (later Roger) McGuinn; Parsons was one of his eventual replacements. Both went on to make albums (The Gilded Palace of Sin; The Fantastic Expedition of Dillard & Clark) that are cornerstones of country-rock – what Parsons called 'Cosmic American Music'.

Parsons died young, at 26; a macabre story surrounding the theft of his corpse cemented his legend. Clark was 46 when he succumbed to his addictions. He's not as well-known as Parsons – God only knows what Keith Richards would say. 'Whenever Keith is asked about his friend Gram Parsons,' Richard Hell says, in an excellent essay, 'he always remarks on how impressed he is by the way people are interested in Parsons even though he never made a hit record. Richards can't think of public respect for his rock and roll peers except in categories of record sales.' But while Parsons was fortunate, as well as gifted, for much of his life, Clark had rotten luck out of the gate.

As the Byrds' primary songwriter, which he was all the way until 'Eight Miles High', Clark received most of the group's publishing royalties, which seems to have led to a lot of resentment, especially after David Crosby joined the band. Clark was fragile, bullied by some of his bandmates, and given to stage fright, crippling panic attacks and (an irony not lost on others) aviophobia. In 1966, he left the Byrds.

Gene Clark with the Gosdin Brothers came out the following year. The Gosdins were good country singers, but this was supposed to be Clark's solo debut; he'd wanted to call it Harold Eugene Clark but bowed to record company demands. The truth is, 'Tried So Hard' and a few other songs are brilliant in ways the rest of the album can't match. But, had the album been better, it might not have mattered: Clark was still signed to Columbia Records, which released the Byrds' new album the same week, threw its weight behind the latter, and left Clark to dangle.

He rejoined the Byrds for a couple of shows, white-knuckled it through a few plane rides, then joined up with Doug Dillard, a Missouri banjo player who'd ended up in Andy Griffith's Mayberry.

Griffith's town was a mirage, but Dillard was the real deal. The music Clark made with him was sublime. But Dillard, who died in 2012, was a hard man to keep up with. 'When Gene got with Douglas Dillard things changed,' Jim Dickson recalled:

Douglas was amazing. He came into town on a vodka drunk, then discovered grass, and kept drinking and doing grass. Then he discovered acid and you would find Douglas drinking, smoking dope, and doing LSD at the same time. How he survived it, I have no idea. But he's fine now. Sweetheart of a guy, but he had an influence on Gene. While it didn't hurt Douglas because he didn't care, Gene was way too high-strung and too complex to deal with that.

Clark and Dillard tried to perform the material in public, but Clark was too wasted to play it. A follow-up album had magnificent moments but fell far short of the first. The 1970s happened: Clark continued to write and record and drink and smoke and do drugs. His marriage collapsed, though the music held up: 'With Tomorrow', 'White Light', 'One in a Hundred' and 'For a Spanish Guitar' from White Light, which came out in 1971 (the record company forgot to print the album's title on its cover sleeve); 'Here Tonight', 'Full Circle' and 'She Don't Care About Time' from Roadmaster, which came out in 1973 (in butchered form, and only in the Netherlands); 'Silver Raven', 'From a Silver Phial', 'The True One', 'Some Misunderstanding' and pretty much everything else on No Other, an album that David Geffen hated, and refused to promote, on his Asylum label in 1974.

Comparisons fail. These songs don't hold their own with Gram Parsons, or with Neil Young or Bob Dylan; they carve their own, canyon-sized niche.

By Keith Richards's reckoning, it doesn't matter: Clark's records went nowhere. There were more songs and more albums, more high points and low points, and all of the wear and tear that had started to show. Clark's health gave out. He had ulcers, kept drinking, and had to have some of his innards removed. He was more or less broke now and more or less sober, and things began to look up for a while. Then Tom Petty covered 'I'll Feel A Whole Lot Better', which Clark had written when he was a Byrd. Clark cashed the royalty check, went on a bender, and died.

All of this happened a long time ago, and most of the people involved are at peace. Clark was buried, back home in Missouri, in 1991. But his recordings keep seeping into the world. Outtakes, but also demo recordings, alternates, and unreleased songs and sketches. He was always prolific. At the weekend, on Record Store Day, Entrée Records released a limited edition EP of songs that Clark cut in 1967 and 1968. (In 2016, Entrée's affiliate label, Sierra, released Gene Clark: The Lost Studio Sessions 1964-1982). In June, another record, Gene Clark Sings For You, will come out. All of this music is worth listening to. At its best, it is transcendent – a chalky, coal-coloured outline of deep, dark American things.