What went so right for the BBC's 6 Music?

Sunday morning in the blue studio at Radio 6 Music, Western House, central London, and Cerys Matthews casts her eye over a stack of e-mails, in preparation for the day's show. "Hey Cerys," the first reads, "I've written before, you are the best and the only radio show I listen to. Requests today: any early jazz, punk, Delta blues, Krautrock (which I must admit I didn't know much about until your brilliant show last week!)."

For two hours each Sunday morning, Matthews's Welsh lilt is the voice of Britain's biggest digital-only music station, joining a chorus of presenters from Jarvis Cocker and Lauren Laverne to Steve Lamacq and Mark Radcliffe, who beguile listeners with a very particular style of intelligent chit-chat and mind-boggling musical range. It's hard to believe, watching Matthews flick through all her fan-mail and requests – "For some unexplained reason I'd love to hear 'Easy to Slip' by Little Feat, any chance?" and "Sundays wouldn't be Sundays without you!" – that not long ago, BBC Radio 6 Music had its head on the block.

In February 2010, word got out that, in order to placate its trustees and free up space for its more commercial ventures, the BBC was planning to switch off 6 Music – a dedicated alternative music station, which, since its launch eight years earlier, had failed to make much of a splash, with a mere 675,000 weekly listeners (compared to Radio 2's eight million and Radio 1's seven million). Given the pressure for cuts across the BBC at that point, you can imagine the thinking of management. This was the year of manufactured pop, of X Factor and Disney-sponsored singing stars, of Jedward and the Jonas Brothers. Who would miss 6 Music, with its menu of dad-rock and obscure folk?

Yet within hours after reports of the planned cuts, a minor revolution swept the internet. Over the next 12 weeks, while the BBC board appeared to dither, public backlash increased. Cerys Matthews led a crusade to save the "slaughtered lamb". Some 180,000 users joined the 'Save 6 Music' Facebook cavalry, while #save6music refused to stop trending on Twitter. There were cyber petitions, and round-robins, and websites launched; anguished pleas filtering through to the real world, too, with David Bowie and Glastonbury's Emily Eavis jumping aboard the cause célèbre.

Musician Dan Bull penned a tuneful protest, "Dear Auntie" ("You need to appeal/ To the people that feel John Peel/ And want to keep it real/ So pretty Beeb, we appeal for a new deal"). The British Association of Songwriters, Composers and Authors (BASCA) issued an open letter pleading that, if 6 Music were to close, a generation of music-lovers would be left "disenfranchised".

Eventually, the BBC had little choice but to listen. As it turned out, at a moment dominated by shiny manufactured pop, this niche station – one that proudly has no prescribed 'playlist', unlike most of its rivals – represented a last bastion of alternative music, and that wasn't something fans were willing to let go. In the intervening two years, 6 Music has tripled its popularity, and now approaches its 10th birthday with a solid 1.4 million listeners. And somehow it's done that while, as Tim Noakes, music editor at Dazed & Confused, puts it "appealing to hipsters and housewives alike without coming off as disingenuous". So where did it all go so right?

A big part of the station's resurgence is due to its presenters. Charismatic, mouthy and possessing extreme musical credibility, Cerys Matthews is the archetype of the 6 Music DJ. On the morning we meet, she wears beige pixie boots, black leggings with big, grey, suede patches, a white T-shirt with stencil of a gold 'Mr T'-style chain, a crumpled white shirt, pork pie hat and a black neckerchief. She arrives heaving several bags, something that looks like a pizza box, and a ukulele – one of a number of toy guitars and ukes she has signed by her favourite artists. This morning her studio guest and musical hero, Irish folk legend Christy Moore, will add his autograph, next to Bob Dylan and Michael Jackson.

Matthews flicks through her track-list for the day, which she's composed over the course of the week, opening with Booker T and the MGs "Soul Limbo" and culminating in Velvet Underground's "Sticking With You", via Senor Coconut and Lana Del Rey. She has lined the studio walls with her rotating, weekly 'wall of fame' vinyl collection, which this week features Bunk Johnson and his New Orleans Band, Ishilan N-Tenere, guitar music from Western Sawel and Richard Burton, a Personal Anthology; transported in the box – not in fact a pizza box but a cardboard record case: "It helps me think".

She's exactly what listeners have come to expect from the 6 Music presenters: smart and quirky, combining musical knowledge and an authentic voice with an impressive bank of trivia, which she reels off at will – "that's not actually a flute, it's a mellotron" – in her winsome drawl. Since her rise to fame in the early 1990s as the bolshy frontwoman of Britpop band Catatonia, she's had various personas, including one as the most unlikely contestant on I'm a Celebrity... Get Me Out of Here (2007), and one who did a duet with Aled Jones.

But it was her time spent in Nashville, Tennessee – where she spent six years "careering around America looking for gravestones of people like Robert Johnson, with only the radio for company, listening to the different dialects, eating catfish burgers" after Catatonia split in 2001 – that have most influenced her Sunday morning radio show.

In Tennessee, Matthews worked with some of the best country blues musicians in the world, not least Johnny Cash's bass player, Dave Roe, hanging out at Bucky Baxter's studio, building an extensive personal archive of country-blues. She brings all this to her show, digging into her endless archive. It's the freedom the station gives its DJs to choose their own music – and in particular to invite musicians of their choice to perform in the studio – that she says makes the station "so important". No one else is doing that, she says – "we need to be archiving these musicians for the future".

Radio 6 Music has had a bumpy first decade, but some aspects, such as the choice of DJs, have always just worked. The BBC launched its new project on 11 March 2002, setting the tone with a morning show from comedian, musical know-it-all and broadcast connoisseur Phill Jupitus. For the first music channel the organisation had launched in 32 years, it assembled a stellar line-up of comics and musos, including Guy Garvey of Elbow and Craig Charles. It was a promising start. After all, just consider the competition: Radio 1 and its commercial peers, all hidebound to mainstream pop playlists and irritating 'banter'; the terminally MOR Radio 2; niche music stations that offered uneven schedules; talk radio and sport stations that broadcast a less-than-progressive worldview.

Naturally, there were ups and downs along the way, such as in 2008 when the then-BBC controller Lesley Douglas – who resigned later that year over the Russell Brand/Jonathan Ross debacle – suggested that men responded to music in an intellectual way while women responding emotionally, in defending her decision to re-jig the Radio 6 Music schedule in order to attract more female listeners.

But the biggest problem, says Bob Shennan, controller of 6 Music since 2009, was that for the first seven years of its life, the station just didn't know what it was: "It had been struggling to articulate its place in the market," he admits, with the result being that it was "bumbling around with about half a million listeners". This left it vulnerable when the BBC began its spending review.

But Shennan believes that Radio 6 eventually found its voice, and believes that in a market saturated by manufactured pop, "audiences are hungrier than ever for an antidote to all that, for something more authentic". The threat of closure in 2010 in fact helped to galvanise its sense of purpose. "It both raised the profile of the channel and helped everybody involved clarify their purpose, and remit. It was a real tipping point," Shennan recalls.

Jeff Smith, who'd been drafted in from other parts of the BBC three years previously to take the mantle as Head of Music at Radio 6 Music and Radio 2 (he introduced the live Evening Sessions at Radio 1 with Jo Whiley and Steve Lamacq) agrees that out of the threat came a clear formula for the station: "to expose a massive range of music, from past and present day, most of which you won't hear anywhere else". The station also took the trouble to get to know its listener. "We're still very much aimed at the over-thirties market – our average listener is a 39-year-old man," Smith says. "If we're now considered cool then that's great but it was not the intention." Nostalgia also plays a part. Tim Noakes agrees that Radio 6 "strives to expose fresh alternative music in new ways, while also educating listeners on rare records from days gone by".

For all its increase in popularity, the station is never going to be mainstream. "That's not what we're about", Smith insists. He may not have a choice. Perhaps it's this indifference, like a hard-to-get lover, that continues to attract attention from so many corners.

In some respects the story of 6 Music, which spreads its best presenters across the day's schedules rather than 'clustering' its talent at, say, rush hour or at breakfast time, represents a wider trend in the way digital listeners use radio. Commissioners of the digital-only stations are finding that their fans are tuning in for longer than traditional FM listeners, and at any time of day or night on iPods and laptops. With the help of playback functions like iPlayer, listeners can pick up their favourite shows whenever they want, breaking all the old rules of scheduling. Changing listening habits may have helped 6 Music to a degree, but Bob Shennan lays the glory at the doors of presenters like Matthews, music personalities who have something unique to offer the public.

From the start, DJs like Adam and Joe (who went on indefinite sabbatical last year) won the station numerous prestigious industry awards, as well as die-hard fans. Now, having honed its line-up, with the likes of Cocker, Laverne and Matthews representing a new wave of unique, informed voices who've joined original cast members – not least Guy Garvey and Sean Rowley – 6 Music has risen from cult favourite to one of the success stories of the digital medium.

So what does the next decade have in store? Does Shennan worry that in a world where people can download an endless supply at the click of the button, that his business might become obsolete? On the contrary: precisely because there's so much music around, the network controller says, radio has a bigger responsibility than ever to help sift through the layers. "Our presenters act as trusted guides, that can help advise, interpret and recommend," Shennan says. "Listeners want someone they can trust to make sense of an extraordinary array of choice."

But for now, there are pressing matters to attend to, like preparing for Friday's big birthday bash at the Southbank Centre, where Laura Marling and Lianne La Havas – just two of the younger artists 6 Music have championed over the years – join Paul Weller and Public Enemy for a suitably eclectic line-up. As for future plans, Shennan assures us, the station is planning to keep on broadcasting "more of the same", which should keep its loyal, passionate – and ever-growing – listening public content.

THE STARS OF 6 MUSIC

Huey Morgan

The former Fun Lovin' Criminals frontman now helms his own weekend slot, The Huey Show, which sees him rolling out 'Sunday jams' in his characteristic American drawl.

Lauren Laverne

Indie poster girl and unpretentious culture vulture, Lauren Laverne has been at the station since replacing blokey George Lamb in 2009.

Jarvis Cocker

Is there a sound on radio more soothing than Jarvis's dulcet tones? During his afternoon Sunday Service, the Pulp singer mixes unlikely records with poetry, stories and gentle musings.

Craig Charles

The comedian and actor, perhaps still best known for starring in Red Dwarf, is a long-time resident at 6 Music: he was there from the beginning, spinning the grooves on his Funk and Soul show.

Guy Garvey

The Northern tones and musical tastes of the Elbow frontman were a natural fit at the station, where he hosts Guy Garvey's Finest Hour (it's actually 120 minutes, but who's counting?).

Shaun Keaveny

In the breakfast slot, another Northerner – Shaun Keaveny, who's been jovially waking a nation of discerning music lovers since 2007.

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The Jam The Eton Rifles