It’s often said that football and music offer the two best escape routes out of poverty but, for the street musicians of Staff Benda Bilili, neither looked likely to offer salvation. Having grown up suffering from polio, the band’s four core members spend their days in customised wheelchair tricycles that provide them with mobility, and their nights pass as they sleep in the grounds of the local zoo. Football was never much of an option to these fifty-something paraplegics, and as citizens of the Democratic Republic of Congo, home to the world’s most deadly conflict since World War II, nor were they ever likely to be groomed for the world’s pop charts.

But that was before the intervention of two documentary makers from France, Renaud Barret and Florent de la Tullaye. Whilst filming Jupiter’s Dance, a documentary about urban music on the streets of DCR’s capital, Kinshasa, they stumbled upon the collective and recognised in them an extraordinary talent. "Their music went straight to our hearts," Barret says early on during this second documentary, Benda Bilili!. Impressed by their "talent and unwavering optimism," they took on the role of deus ex machina, making it their goal to help the band on the road to global fame. "It got us thinking," he continues. "It wouldn’t take much to help them record an album. So we decided to do just that with our own money. For these disabled, veteran street musicians, we presented an opportunity not to be missed."

It’s a rare moment of self-congratulation from two men who have, without a doubt, helped transform the lives of a band that would most likely have otherwise remained where they were. Kinshasa may be a safer city than the border area to the east close to Rwanda, where genocide has claimed the lives of millions, but it’s far from welcoming, as the second scene, shot by night, highlights. Against the silhouettes of cars and fumes, the voice of a street kid is heard: "That guy filming us, I could easily steal his bag. And the millions inside it. And I’ll take the camera he’s holding too. I don’t mind being a thief. Any 12 year old living on the streets should do that… Kids don’t have a choice. You sleep outside. You suffer from the cold. This country is screwed."

The filmmakers’ explanation provides a necessary moment of exposition, dealt with sensitively and immediately balanced by a brief scene that shows the musicians’ initial wariness at the possibility of being exploited. But it’s also indicative of the modesty that the directors exhibit throughout this wonderful documentary. In taking on the responsibility of helping make dreams come true, they’re playing with more than the average hopes of your suburban indie kid, or the karaoke singer looking for a shot at fame. Barret and de la Tullaye must have known that any decision to involve themselves would have to take into account far more than whether what ensued might make for great cinema, and so they don’t seek applause for their actions, instead ensuring that Staff Benda Bilili remain the true stars, because, as Ricky, the anointed head of the group points out, there’s far more at stake than for most developing acts.

"I’m working for our children’s future," he explains. "If I die, what will I be leaving them? A sewing machine. They won’t have anything, not even a roof over their heads. With the music I’ve composed, it’s different. If it’s successful in Europe, it’ll bring in money every year. My kids will be saved."

Benda Bilili! joins the band for the best part of five years, from their initial discovery to their eventual journey to Europe. The success of ‘Anvil’ has shown that there’s a market for films that depict music as a means of escape from poverty, especially those with a happy ending, but if that film proved heartwarming and provided the metallers with a novel leg-up back onto the ladder towards stardom, Benda Bilili! puts it in the shade. Sure, Anvil had to overcome a number of setbacks during the course of their lives, and as the film began its two main protagonists were carving out meagre livings working as a truck driver and construction worker. But these are nothing in comparison to the obstacles that lie between Staff Benda Bilili and success. A brief scene in which they celebrate finally owning their own passports does much to highlight just how far their existence is from recognisable Western lifestyles. The self-belief of the Staff, however, is not easily crushed. They recognise that they have a unique chance to lift themselves, and their family, out of the gutter, and their determination is breathtaking. "I used to sleep on cardboard," they sing joyfully in an early scene. "Bingo! I bought a mattress. It could happen to you. A man’s life is never over. It’s never too late in life. I know we’ll succeed one day."

The obstacles they face would be enough to knock any hope out of most people, however, and all around them one can see how life has taken its toll on others. Though little background to Congo’s recent turbulent history is offered, much in keeping with the documentary’s attempt not to tug the heartstrings too blatantly, the camera can’t hide the grime of streets where fires burn by night to warm the residents, or the battered shells of trains overflowing with passengers, many of them clinging to the outside, or the van in which they drive to the airport, windows merely holes carved out of its metal sides. And yet somehow they’ve found a way to celebrate life with their music, and the sheer delight in their faces as they play contrasts brutally with their surroundings. Even after the official shelter they’ve been spending time in burns down to the ground, sending them and all its inhabitants back to the streets and causing the band to break up soon afterwards, they eventually reconvene – after Ricky has travelled far and wide on crutches, collecting one member from his village in the Lower Congo – to sing together once more of how, "the ground you walk on is full of gold and diamonds".

What’s most striking about this remarkable group, however – apart from the fact they make a form of music that is not only wildly uplifting but genuinely original in its mixture of musical styles and instrumentation, irrelevant of its genesis – is the responsibility that they place upon their own shoulders. Their songs cover themes arguably never addressed in such a forum before: one encourages mothers to get their children vaccinated against Polio since, as Ricky puts it, he’s now "screwed to his tricycle". Another encouraged people to vote during the 2006 elections, the country’s first multi-party ballots in almost 50 years. (In fact – though this is not addressed during the film – the song was used in a film designed to boost voter turnout by the UN Development Programme, who allegedly paid the musicians $50 and failed to credit them at all. Indefatigable as ever, the band are currently suing for payment through the courts.) They practise what they preach, too: "I’m a street Daddy," Ricky says to a local youth at one point, "and you’re a street kid. So how are we different?" When the youngster points out, "You have music," Ricky promptly hires him as a dancer.

As the possibilities of success hover within their reach, expectations placed upon them by those close to the group weigh them down with even further responsibility. New arrival Roger – another street kid who won a place in the band thanks to his unusual ability to play the satonge, an instrument he built from a tin can, a bent piece of wood and a length of electric cable – is given a thorough dressing down by his family upon the eve of his departure to Europe: "If you fail, it’ll kill me," his mother tells him, while his sister adds, "We’re counting on you… It’s up to you to do your best to feed your family." This, presumably, is a problem that Mumford & Sons never faced.

Spliff in hand, leaning back on their tricycles, two band members celebrate the completion of the record by dreaming of the response that lies ahead of them. "The new sound of the world," one of them smiles. "The world’s new idol is Staff Benda Bilili. It will be the event. Never in the history of the world has this been seen." And with their first concert off the streets, at Kinshasa’s French Cultural Centre – to celebrate the European release of the album – there’s an undeniable sense that this fantasy is now within their grasp as they perform a vibrant, eye-poppingly energetic show that not only brings the real life audience to its feet but also brings goose bumps to the skin. That it also helps get Roger’s mother out of hospital, something that Ricky insists upon as he passes the youngster his share of the (significant) fee, makes it even more affecting.

What’s perhaps most wonderful about Benda Bilili! is that it tells, in many senses, a fairy tale that’s entirely true. It could have been horribly patronising, of course: the white men come to Africa and save the poor natives from their fate, the world subsequently embraces the paraplegics because they smile a lot, crack mischievous jokes about weed, and do their best to make the world a better place against all the odds. No one actually needs to listen to the sometimes-tragic lyrics, after all, since they’re sung in a foreign dialect. But instead what the film highlights is that music is a universal force capable of bringing communities together, able to empower them, not just in small groups but en masse. This in itself is a welcome reminder why musicians should be paid for their craft, and the film provides a fantastic showcase for Staff Benda Bilili’s music while telling a genuinely moving story in a succinct, powerful fashion. It also emphasises that sometimes it takes only self-belief, talent, courage, a little luck and a belief in human kindness to make a difference. Few of these are out of reach for most of us, but for crippled homeless veterans in arguably the world’s most dangerous country, they’re further than we could ever imagine.

Millions remain in Kinshasa, of course, unable to escape the squalor and violence of a country that is "screwed", and Barret and de la Tullaye are not foolish enough to suggest that their happy Hollywood ending is indicative of the fate awaiting the rest of the country. A phone call comparing the climates of Scandinavia and their home to relatives in Kinshasa emphasises how they have left families behind, as well as the power they now wield to help them. An escape route like this is obviously the exception rather than the norm. But it’s gratifying to see genuinely talented musicians rewarded for their work rather than identikit individuals plucked out of a line-up for their camera-friendly looks and ability to carry a simple melody. And on the evidence of this film, Staff Benda Bilili are more than deserving of the success that they now enjoy, their humility as inspirational as their music. If you think your life is hard, hand over your cash for this film, buy the album, and then, quite simply, shut up, listen and dance.