It can be quite easy to be sceptical about the endless wave of deluxe reissues that come Uncut’s way most weeks: classic, economical albums stretched over two discs, full of variegated b-sides and out-takes that rarely add much to an artist’s story, really. I am, of course, a big enough nerd to get excited about, say, the juggled alternate mix of Love’s “Forever Changes” that arrived recently. But to be honest, listening to this stuff is like watching a good documentary on BBC4; at the end of it, I feel like I know more about an esoteric corner of history, but I hardly need to watch it again.

And so I have shelves of bonus discs at home that we could refer to euphemistically as “research resources”. I don’t quite ascribe to the hardline approach of someone like Lawrence from Felt, Denim and so on, who believes that any extra tracks compromise the artistic purity of an album, but I can certainly see his point.

Then something comes along with a bonus disc that harbours music I’ve craved for years, and the whole racket is justified. Dennis Wilson’s “Pacific Ocean Blue” has been unavailable for years, which is obviously a fantastic reason for a CD reissue. But the usefulness of this Epic/Legacy project is intensified by the appearance on Disc 2 of “Bambu”, Wilson’s follow-up, and one of those mythical unreleased albums that measures up to the musty record collector hype which has long surrounded it.

For the most part, the “Bambu” songs, recorded through 1977 and ’78, are woozy expansions on Dennis Wilson’s long-time aesthetic – a sort of gruff etherealism, with songs staggering away from easy resolutions, privileging atmospherics over simple hooks. “I Love You” is chiefly plangent piano and soaring, wordless harmonies – two elements which are hardly new territory for a Beach Boy, but which here are given a fractured, classical aura.

A damaged grandeur dominates, with epic arrangements contrasting with the degraded nature of Wilson’s vocals. Always husky, at least compared with the saintly tones of his brothers, Wilson’s voice is enormously battered on the likes of the featherlight melodramas of “Love Remember Me”, “It’s Not Too Late” and “Are You Real”. The music is cloudy, meticulously scored yet somehow imprecise, a kind of amorphous rethink of late ‘70s AOR; something here called “Album Tag Song” (on my promo, at least) seems to move towards a gently pulsating kind of prog MOR.

Even on the rockers like “Under The Moonlight” (someone here just mentioned Nilsson’s “Pussycats”, appositely), Wilson sounds exhausted. But without fetishising an artist’s physical and mental strife too much, it is his weary effort that makes the track so gripping, moves it away from retro rock’n’roll vamping and towards something odder and more affecting. The Hawaiian shirt flash of “Constant Companion” works similarly. Between the parping horns and snazzy rhythms, you half-expect Jimmy Buffett to emerge, brandishing a cocktail with a sparkler in it. Then Wilson arrives, bedraggled.

You can see why the record was never released, not least because of these uneasy commercial juxtapositions: the life and soul of the party sobbing into his margarita. At the same time, remember, The Beach Boys were trying manfully to cash in on the disco scene with “Here Comes The Night”, scrupulously hiding all the messy stuff as best they could. But artistically, “Bambu” is slow dynamite, and the perfect complement to “Pacific Ocean Blue”.

Which comes, as well, with a few out-takes including one, “Tug Of Love (Feel The Pull)”, that may be one of the best examples of Wilson’s transcendent-sigh schtick I’ve come across. And with an unfinished demo, “Holy Man”, that has been finished with the addition of a vocal by Taylor Hawkins, the Foo Fighters drummer, and an uncanny mimic of Wilson’s harmonious croak. Clever, but I don’t really see the point. Maybe, in this case, the desire to finish something unfinished has been taken a little too far. . .