Here we go again. Tomorrow sees the release in UK cinemas of I’m Your Man, a widely praised, strikingly redundant feature film about Leonard Cohen, in which a succession of younger musicians come forward to re-emphasise the point that the 71-year-old Canadian singer-songwriter is just great, you know. They then try to prove this by performing some of his tunes.

Largely threaded around a concert that was filmed in Sydney in January 2005, I’m Your Man is interesting for all the wrong reasons. In the first place, it serves as a reminder that nobody can sing these songs better than the old grumbler, Cohen himself. It’s precisely because he refrains from fluffing up the vocals of Chelsea Hotel and Everybody Knows, the way Rufus Wainwright does, that the pathos and the ironies in the lyrics shine through.

Similarly, if he’d wanted to distract us from the superbly droll drift of Tower of Song, he couldn’t have done better than to get U2 to play along — with the Edge on slide guitar and Bono rather prominent on backing vocals — in a cosy, stellar finale that falls sadly flat. Beth Orton’s version of Sisters of Mercy is one of the better moments, mainly because she looks and sounds far too terrified to try anything on. Meanwhile, Nick Cave, who gives I’m Your Man his best shot, seems to be impersonating the fruity drawl of Frank Sinatra.

Why, when the time comes to pay tribute to one of the acknowledged masters of popular music, is it always the youngsters who are drafted in to do the business? I’m Your Man is trundling along a track almost identical to that of the 1991 Cohen covers album I’m Your Fan, on which indie favourites such as Pixies and James stepped up to the microphone, with similarly mixed results.

The opportunities thus created are clearly as much about the marketing of such ventures as the music. Cohen’s wordy approach to song is more widely shared by the performers of his own generation — the folkish musicians who grew up with the Beat poets in the 1950s — than by those who came after rock blasted its way into the consciousness of youth, blunting the semantic thrust of what was being sung about with loud guitars and vocal pyrotechnics. What a shame I’m Your Man couldn’t have engaged the services of Neil Young or Bob Dylan.

Part of the difficulty in getting hold of those two lies in the fact that they are also being basted in adoration by the younger rock fan. With the resurgence of teenage interest in guitar bands has come an accompanying spasm of ancestor worship. Dylan’s pretty average recent album Modern Times has been talked up as a work of genius on a par with his genuinely ground-breaking work in the 1960s and 1970s. Likewise, Neil Young’s “metal folk” protest Living with War. Young’s performance movie Heart of Gold, which has just been released on DVD, was filmed by Jonathan Demme in Nashville last year in front of an audience younger, for the most part, than the guys and girls in the band.

The strongest confirmation that this isn’t just another outbreak of symbolic cap-doffing has been the extraordinary commercial success of Tony Bennett’s recent Duets album. As he turned 80, Bennett enjoyed his highest UK chart position in 30 years, and became the oldest artist yet to make the Top 20 in the album charts. In America, Duets made the Top 3, selling faster than anything he had previously put out back home.

It is no surprise to see that many of Bennett’s duet partners on the album are singers who learnt their trade long after the crooning tradition had fallen into decay. But that’s hardly a disincentive for practised tribute-payers such as Bono, George Michael, Michael Bublé, Diana Krall and Elvis Costello. It’s not that they make a bad job of things, exactly, just that the strongest sound is that of mutual back-scratching. It’s a celebrity transaction, basically — which, at this stage in his career, Bennett has no more need of, you would have thought, than Cohen.

And it leaves you wondering: why don’t these youngsters show a bit of disrespect?