'Who wants yesterday's papers?" sang Mick Jagger in one of the Rolling Stones' more callous jibes. He was referring to the disposability of his own girlfriends. Yet the metaphor can serve equally well for the inherent ephemerality of all pop music - not only Jagger's own, but even that of the current sacred cow, Bob Dylan.
Dylan is current only in the sense that he's always been current. The adenoidal folk rocker's heyday may have been a good four decades ago, but his status has remained huge. Yet Martin Scorsese's marathon biographical documentary has created unprecedented excitement around the sixty-something singer-songwriter. The sense of awe it has generated and the apparently universal consensus on Dylan's "greatness" mark a new phase in pop's cultural dominance and in the unreality of the claims made for it.
Where once the fetishistic raking over of the lives and doings of 1960s pop icons was the exclusive province of the specialist music press, it now dominates the mainstream media to the extent that even my 86-year-old father-in-law - a lifelong loather of pop - is starting to wonder if he should take an interest in "this Dylan fellow".
Yet even the best pop music can sustain remarkably little in the way of critical analysis - let alone the endless reinterpretation to which the classics are subjected. But what's worst about the creeping monumentalisation of pop is not just its inherent absurdity, but the way it threatens to smother this music's fragile charms altogether.
We live in a world run by people who came to consciousness during pop's 1960s golden age. Often significantly younger than Dylan, they not only understand the iconic significance of the Fender Stratocaster guitar, they actually own one. It's hardly surprising, then, that the new film's "lost footage" from Dylan's crucial mid-1960s period should have created excitement. Yet there's something about our "air guitar" establishment's endless valorisation of the sounds of its youth that is slightly creepy.
I'm not anti-pop, or even anti-Dylan. His Like a Rolling Stone is one of my favourite pieces of music. Or it was until the American rock critic Greil Marcus decided to write an entire book about it and a panel of rock and film stars voted it the cultural artefact that has most changed the world.
There's something about the very nature of the pop song that makes it unsuited to this kind of clumping endorsement. Pop's roots are in the mercurial joys and anguishes of adolescence. Like a Rolling Stone may be as good as pop gets lyrically, but Dylan's warning to a slumming rich girl doesn't add up to much without his whinily splenetic delivery and the joyous rhythmic surge of the original recording. Once you start weighing it down with a mass of critical baggage, the sparkle goes.
Scorsese's film and Christopher Ricks's often hilarious, convoluted critical tome Dylan's Visions of Sin have reawakened the decades-old debate on Dylan's status as a poet. Yet Dylan's endless namechecking of cultural figures from Dante to Rimbaud amounts to little more than garbled adolescent name-dropping.
Moments of skewed surreal brilliance and nuggets of universal tenderness and wisdom are jumbled in his work with make-weight phrases and cringe-making rhymes. Yet it works as one great shout of post-adolescent self-assertion in which prodigiousness and pretentiousness are all bound up in Dylan's droning and often spectacularly mannered vocal delivery. Once you start to pin Dylan down, it all evaporates.
Indeed, Scorsese's film - a brilliant work - is less an endorsement of Dylan's claims to artistic greatness, than an assertion of just how "pop" he is. Even at his most earnestly folky, Dylan was manicuring his image with a Madonna-like assiduousness. The "lost" footage of his seminal, mid-1960s period, when he supposedly changed the world, reveals the poet and prophet to have been an actor and a rock 'n' roll poseur to rival David Bowie and Mick Jagger at their most flamboyant.
Dylan is undoubtedly a genius, but he's a pop genius. He's got more in common with Kylie Minogue than with Beethoven, and like all pop geniuses he has manifestly failed to carry his greatness into the starker territory of middle age.
So will we still be furiously discussing Dylan's literary standing in 50 years' time? I doubt it. Not only will our current preoccupation with Dylan's historical moment have long since faded, but we'll have learnt to accept that something can be "great", but still part of a popular, oral tradition that may be as disposable as Mick Jagger's newspapers.