(director Andrew Sharper and producer Joel Rassmussen, still mulling over an adaption of “Tits Out Teenage Terror Totty”)

Not content with bashing poor old Dave O’Brien or trashing Ben Franklin, the Guardian’s Steve Wells turns his withering worldview to the documentary “Before The Music Dies”, a film that purports to show how “a once radical art form has been reduced to a marketing tool for tampons.”

It’s not that B4MD (as it cutely calls itself) doesn’t do a good job teaching your granny how to suck eggs – the sections on the deregulation-driven homogenization of US pop radio is particularly chilling. And its impossible to fault the film’s argument that capitalism destroys the very culture it seeks to exploit. It’s just that nearly all the “real” musicians it trots out as the credible alternative to the likes of Ashlee Simpson suck like a prolapsing white dwarf star.

The featured performances are – with a few exceptions -awful. Horny-handed sloggers like the Dave Matthews Band, North Mississippi AllStars and Dave Hidalgo trudge through nightmarishly long retro-rock jam sessions.

But the most irritating part of B4MD is when it sneers at the fans of manufactured music. “Has Ashlee Simpson ever inspired you to do anything?” the interviewer asks a brace of teenage girls. Has Dave Mathews? To do what? Buy a shed?

The film-makers then prove how easy it is to make a manufactured pop hit by getting a beautiful teenage girl to record a tune casually bashed out by a 45-year-old male songwriter. The result is mediocre. But with the exception of performances by a young Billy Preston and the wonderful Erykah Badu, it’s the only music in the movie that doesn’t make you want to stick pencils in your ears.

Before the Music Dies is Grumpy Old Men for musos. The film’s largely unexamined assumption that music is going to hell in a handbasket puts one in mind of an old Ray Lowry cartoon: Two aged sex-goths in Rancid Hell Spawn and Alien Sex Fiend T-shirts stare in disgust at young girls flocking to a Take That concert. “I remember when it were all Fields of the Nephilim around here,” says one.

Of course, the rock jokes were much better back then.