Gwyneth Paltrow's movie Country Strong sings the blues

Gwyneth Paltrow's turn as a singer in Country Strong has floundered critically and commercially, but what makes a great fictitious musician? From Spinal Tap to Bill & Ted, we look at the hits and the misses.

Critics didn't buy Gwyneth Paltrow's new movie, Country Strong, writes Ben East, so which fictitious musicians have scored hits?

As films set in the world of country music go, Gwyneth Paltrow's latest movie appears to be, in the words of the 1964 Johnny Cash song, Bad News. Country Strong, in which Paltrow plays a fragile, troubled Nashville star hoping for one last shot at the big time, certainly sounds like it contains all the ingredients for emotive drama. But the critics were decidedly less impressed. The New York Times moaned that it suffered from an "absence of detail, texture, life". The script doesn't "shy away from coincidence or predictability" said Variety, and the "story is sillier - and more tone-deaf - than Paltrow's advice website", mocked Village Voice.

Unsurprisingly, Country Strong has not been a huge success at the US box office, although most critics were pleasantly surprised by Paltrow's portrayal of a faded country star - if not the vehicle she stars in. But then, her latest project was always going to be a gamble. Making up a convincing fictitious band and asking an audience to both like their songs and believe in their story is by no means an easy task - as anyone who endured the noise made by Wyld Stallyns (the group Bill & Ted front in their Excellent Adventure) will attest. After all, there have been enough enjoyable and revealing biopics about real-life musicians in recent years - Walk The Line (Johnny Cash), Ray (Ray Charles), Control (Joy Division) - to make the prospect of investing in the lives of rock'n'roll stars who don't even exist seem a little pointless.

Country Strong had a problem right from the start, however. And that was the presence of another film that similarly wallows in the downbeat world of a fictional country music star - but combined the right music with the right story in spectacular fashion. Jeff Bridges was perfectly cast in Crazy Heart as a world-weary, down-on-his-luck country musician, and his languid performance won him an Oscar for Best Actor. It was also telling that the Best Original Song gong went to a track from the film too: Ryan Bingham and T-Bone Burnett's The Weary Kind. Rightly so: the melancholy sound perfectly matched the feel of the film.

Of course, you'd hope Bingham could come up with an instantly memorable tune - he's a country music songwriter of some note in real life. But it definitely helped that Bridges performed the songs in the film himself, imbuing both the music and the tale with rough-hewn earthiness and believability.

Having T-Bone Burnett on board also helped matters - in 2000 he produced the multimillion-selling bluegrass soundtrack to O Brother, Where Art Thou. It's not strictly a film about a fictional band, but a crucial plot development sees the trio of chain-gang escapees come across a young guitarist. Together, they record as The Soggy Bottom Boys, at a radio station owned by - as this is a Coen Brothers film - a strange blind man. Sadly, George Clooney, as the escapee Ulysses Everett McGill, was only miming. But proof that The Soggy Bottom Boys had been a persuasive act came with a subsequent American tour by the musicians who actually performed the songs.

But The Soggy Bottom Boys have a long way to go before they match the most famous fictitious band ever: Spinal Tap. The rock mockumentary in which they starred, This Is Spinal Tap, was such a brilliant satire of the ridiculous excesses of heavy metal, the director Rob Reiner had to remind people that this wasn't a real band at all. Indeed, several real-life rock bands failed to find the funny side back in 1984 (particularly Aerosmith, who thought it a little too close to home). But for everyone else, it didn't just skewer the pathetically needy existence of rock stars, it also contained some of the best parody songs ever created - which is why, 25 years later, the spoof British metal band sold out venues across the world when they went on an anniversary tour. And the film worked because it contained just enough truth to be plausible. In fact, too much for some: Noel Gallagher once remarked (with some glee) that his brother in Oasis, Liam, had once stormed out of a Spinal Tap live show after getting sick of the jokes. He had believed to that point that Spinal Tap were a real band and the film a no-holds-barred documentary.

To be fair to Liam Gallagher, it's an easy mistake to make. After all, The Monkees started out as a fictional television series about a Beatles-esque foursome, recorded albums and made a feature film, and ended up becoming a real group. It became genuinely difficult to know whether Davy Jones, Mike Nesmith, Micky Dolenz and Peter Tork were playing at being a band or were actually in one. In the end it was the latter - and the songs have endured.

Of course, there's another way to fashion a convincing fictional band: have them sing songs we already know, but in believable contexts. The Commitments did this in fine style in Alan Parker's gritty black comedy with real heart and soul about an Irish covers band. And while The Blues Brothers might be a little more fantastical, when John Belushi cranks out the classics, it's great fun.

Such films work because the songs provide the backbone to the story. It's why Cameron Crowe's semi-autobiographical Almost Famous - in which the rock group Stillwater are a note-perfect combination of the likes of The Eagles and Led Zeppelin - has lasted and Todd Haynes's glam-rock film Velvet Goldmine hasn't. We're asked to believe in a protagonist who is clearly a thinly-veiled David Bowie - but without the tunes to match.

Country Strong's songs aren't that bad. They conform to all the country clichés - but then, so does the film. And that's the problem - the best movies starring fictitious bands don't just throw together a whole load of stereotypes and hope they stick. They're a finely tuned amalgam of good music and believable stories. As David St Hubbins says in Spinal Tap: "It's such a fine line, between stupid and clever."