Sharon Shannon has been a superstar of Irish folk for nearly 40 years – but beyond her status as the Beethoven of the button accordion, how much do we know about her? Less than you might imagine, suggests Tradfluencer – The Sharon Shannon Story (RTÉ One, Monday, 9.35pm), a fascinating portrait of a famous musician who has lived nearly her entire adult life in the public eye while remaining the ultimate blank space, ubiquitous yet unknowable.Shannon is first to admit that she has never been comfortable under the spotlight – an obvious obstacle for someone who has spent so much of their life on stage. At school in Clare, she was a loner. Today she lives alone in Galway – though she does not think of her existence as in any way solitary, given that her house is full of pets. Still, she knows she was not necessarily cut out for the celebrity her talents have brought her in folk circles. “I find it debilitating at times. I don’t know if shyness is the right word,” Shannon says. “Maybe a lack of confidence in how I can articulate myself. It causes me anxiety. That’s a part of my personality I find hard to deal with.” Tradfluencer is two different documentaries sitting side by side. At one level, it is a celebration of Shannon as a pioneering musician who brought a rock’n’roll fervour to the unfashionable button accordion. “She was able to make it squeal and groan and roar,” says U2’s Adam Clayton, who recalls his astonishment at seeing Shannon play the accordion for the first time. “This was a very aggressive vessel she was wrestling with.”She has a talent for leaving a certain sort of musician – shaggy rock stars not necessarily steeped in folk – shaken and stirred. That was certainly the impact on The Waterboys’ Mike Scott. He is moved almost to tears recalling Shannon playing an old Scottish trad tune as he stumbled about, bleary-eyed, the morning after a late-night session in Kinvara. “Sharon plays tunes the way other people breathe,” he says, still struck by that moment all these decades later.But the film finds it harder to get a sense of the person behind the music. That is because Shannon is a low-key individual who communicates through her playing and is slow to let her guard down (as is entirely her right). She keeps the camera at arm’s length when talking about her childhood near the Burren – though she is understandably emotional reflecting on the death in 2008 of her partner Leo Healy, who suffered a fatal heart attack at the age of 46. “You know when they say, ‘I can’t believe such-and-such is dead?’ That is exactly how it feels sometimes. You don’t believe it.”Tradfluencer follows her to Japan, where fans are in awe of her exhilarating playing. Then it’s off to a Shane MacGowan tribute in Wexford, where she is joined by Imelda May, who is invited to talk about Shannon’s importance. As she does so, Shannon beats a hasty retreat – ears burning in embarrassment.“God love her,” laughs May. “She’s not able for the praise at all.” It’s the truest word spoken in a well-intentioned documentary that tries hard, but ultimately fails to give us any real sense of what Shannon is like offstage, with the lights dimmed and the music played out.