David Bowie as Nikola Tesla is a crafty piece of casting. He barely appears in Christopher Nolan's The Prestige, but his elusive character sheds a vast, unifying, enigmatic glow across the film's tortuous narrative.

Tesla was a unique and divisive figure in the early 1900s. All who embraced modernity would listen to his radio in the light of his AC current, though he was variously considered genius, quack, charlatan and showman. A century later, well, let's just say that David Bowie has certainly illuminated a few more corners.

Nearing 60 and playing himself, he looks very much the aged oracle in Wim Wenders' short film,The World's Greatest Record Stores. His once peerless cheekbones are dimpled anchor points for sagging jowls. His hair is a mousy brown coif where crazy styles and colours have come and gone. A black skivvy abdicates his longstanding fashion-icon credentials.

Bowie's voice is weathered too, as he makes comments between a series of interviews with owners of specialist record stores from Sao Paulo to Tokyo, Chicago to Brisbane. "Hearing these people talk about their jobs working in record stores is really exhilarating," he croaks wistfully, like a man watching his youth flash before him in the half-light.

"They're all talking with the same energy about the same subject: just being knocked out by music that you've never heard before. Listening for new things is a real driving force for me, and I know I couldn't have lived my life without that ... Happy listening," he smiles, like a fading, affectionate uncle.

Bowie's strange new gig is in the employ of Nokia, whose portable digital media devices are flourishing like weeds where record shops like these are closing daily. Wenders' film, screened to an invited audience in Melbourne in December, is hence a profoundly ironic advertisement for Nokia's new online initiative, musicrecommenders.com. But from Ziggy Stardust to Nikola Tesla, David Bowie has always been a profoundly ironic kind of guy.

He's the appointed "godfather" of Music Recommenders, a site dedicated to expert, independent advice on new music, continually updated by 40 hip music stores around the world - and Bowie. The role fits him like a black skivvy: he's been a visionary conduit between old and new; obscure and mainstream; difficult and cool sounds and technologies for 51 years.

Well, that long in his dreams. David Robert Jones was nine when his father brought home his first stack of 45s by the Moonglows, Fats Domino, Frankie Lymon and the Teenagers, the Platters, Fats Domino and Little Richard. He told biographer David Buckley he had to play them on a 78 rpm gramophone, spinning them with his finger until they sounded "wonky and wobbly", but about right to his ear. It was a poetic precedent for his future as a cunning manipulator of found sounds.

His penchant for filtering and processing disparate elements from the fringes of popular culture would define Bowie's very particular gift to rock'n'roll come the 1970s. Though often derided by genre purists for his opportunistic dilettantism (Mick Jagger once sniffed "he'd steal your shoes if he thought he could use them in his next show"), he dragged into the mainstream a range of influences that commercial forces might never have entertained.

Most commonly cited are Lou Reed's Velvet Underground and Iggy Pop's Stooges who, without Bowie's recommendations, might never have reached the ears of Sonic Youth, the Pixies, REM, Nirvana and countless other architects of '80s and '90s youth culture. Less often credited is Bowie's brazen appropriation of black soul music with Young Americans circa '75, a chart-topping entree for the Bee Gees' earth-shattering disco crossover.

By that time, he was hearing new music again. The relatively few believers who followed the newly christened Thin White Duke to Berlin were among the first kids to hear NEU!, Kraftwerk and other robotic drones, textures and techniques that would infuse the new romantic, hip-hop and dance music waves of the future.

What was perennially attractive about Bowie was his refusal to make his bed with any of the musical movements he had heard coming. He was the seer, the recommender, the restless agent provocateur, and nobody's dancing monkey.

Under that kind of pressure, it's easy to see why he killed himself off with his ingeniously self-referential Scary Monsters album at the end of the '70s, and why, exhausted and underpaid for his efforts, he opted to pander to the lucrative mainstream with Let's Dance onwards.

Ten years ago, Bowie shrewdly threw his own 50th birthday party at Madison Square Garden. Any interim suggestion that he'd misplaced his currency was roundly refuted by his backing band: Sonic Youth, Foo Fighters, Billy Corgan, Frank Black, Robert Smith ... even estranged '70s comrade Lou Reed turned up to plug in and tug a forelock.

There are no such celebrations planned this weekend. Bowie has kept a low profile since he was hospitalised in Germany in June 2004. We were told it was only a pinched nerve, but a week later he had emergency heart surgery and called an abrupt end to his Reality world tour.

He has posted just seven brief blogs since, and apparently stays close to home on Manhattan's lower east side, where he's rarely photographed at the opening of a play or opera with his wife, Iman, or glimpsed at a gig by Arcade Fire, Deerhoof or TV on the Radio.

"I've never seen (13-piece avant-garde ensemble) Icebreaker," he volunteered to Q magazine in November, "but would drive a mile or more to do that thing."

With convincing portrayals of the elephant man, Pontius Pilate, Andy Warhol and Nikola Tesla behind him, he's about to appear as two cartoon characters, first in Luc Besson's Arthur et les Minimoys, then alongside Spongebob Squarepants.

In May he'll curate New York's inaugural High Line Festival, for which he'll play his first full concert in three years - though there's no sign of a new album since he pronounced himself "fed up with the industry" at the end of a fallow '05. Instead, "I've been particularly excited about seeking out emerging artists and giving them a place in the festival," he says.

And so here he is, a moist-eyed seer in a darkened room, telling Wim Wenders about his undying love for Chicago blues, the fabulous experimental momentum of hip-hop, a wonderful samba version of Ziggy Stardust he heard recently.

Ultimately though, there's also the rather deflating disclaimer that, as far as the rest of his "to-listen-to pile" goes, "there's really not enough time sometimes".

Cripes, not you too, David? Oh well, many happy returns.

Golden years