“You know the one where hell is a bunch of banjos?” Bela Fleck is laughing about his favourite Far Side cartoon down the phone from Memphis, Tennessee.

If you haven’t seen it, the gag is that the devil is ushering a recently deceased conductor into a room full of banjo players — ‘right in here, Maestro’.

This Saturday Fleck plays a concerto with the BBC Scottish Symphony Orchestra as part of Celtic Connections. It’s a piece he wrote — it would be; there aren’t a lot of other banjo concertos in the repertoire — and it’s called The Imposter. Much is packed into in that title. The instrument’s lambasted reputation, centuries of Western musical hierarchy, Fleck’s own family history, even his name.

“It’s kinda good I can laugh about it, right?”

Fleck is America’s banjo luminary. He’s the instrument’s most virtuosic champion; a phenomenal technician who for decades has pushed repertoire boundaries and pilfered from musical styles ranging miles beyond bluegrass. He says he loves the idea of the maligned and humble character fighting for equality on stage against the mighty orchestra.

“The banjo has been treated with such distain over the years,” he sighs, “but really it’s an incredibly strong and primal thing. Skin stretched over gourd, gut over wood. So yeah: banjo guy putting on a tux and strutting out in front of an orchestra? Of course I like that.”

The Imposter isn’t just a subversive prank; Fleck says he spent years summoning the courage to write it. Why the a deep urge to create a score for banjo and orchestra? “Because it hadn’t been done yet,” he answers straight-up. “And because I didn’t see anyone else doing it. Eventually I found the courage because I watched my friend Edgar Meyer write his bass concerto and realised that here was someone I knew doing a thing I thought only dead guys could do.”

If names are auspicious then Fleck is closer than most to those ‘dead guys’. He was christened Bela Anton Leos after Bartok, Webern and Janacek: “we’re not talking any old classical composers but heavyweight modernists,” he groans. “I was named by a father who abandoned me when I was two years old and whom I didn’t know until I forced him to meet when I was in my 40s.” He describes spending much of his life pointedly ignoring the weight of those forenames, never learning to read classical music notation — he wrote The Imposter in banjo tablature then had it transcribed for orchestral players to read. For decades he avoided getting to know the music of Bartok.

“When I finally came to writing The Imposter I was in my 50s. I guess it was my way of making peace with my name. I’ve done loads of different things in my life — worked with people from all around the world, jazz and traditional and all kinds of musicians. My mission seems to be to show the banjo in a different light… I guess I had to face the orchestra at some point.”

He’s keen to stress that The Imposter is no bluegrass concerto: in fact, he “avoided that like the plague".

"Bluegrass would have been so expected. I’m tired of the whole Appalachian cliche; the ‘here comes the hillbilly’ stereotype that goes with banjos. It can all be so damn cheeseballs.”

Instead he immersed himself in Haydn, late Mozart (especially the Jupiter Symphony) and in Bartok’s concertos and solo piano pieces.

“Bartok taught me to be brave, and to embrace dissonance. If you listen to dissonance for a while then it doesn’t sound so crazy any more.”

The first movement of The Imposter is full of audible attempts to appropriate the style of various composers. “You can hear me trying to be all kinds of things, trying to write Bach fugues and so on.” But as the piece goes on, Fleck flings away the pastiche and finds his own voice. He chose not to go back and revise that first movement because, he says, he wanted the process to be audible.

“Total imposter to hopefully-not-such-an-imposter,” he suggests.

Does it work? Does the banjo put up a proud fight against the orchestra? To get the balance right Fleck has to amplify the instrument slightly — “there’s no point not being heard, and there’s no point writing the orchestral parts so thin that I couldn’t make use of the forces on stage”. But he’s satisfied that the power play is still there: “little banjo, mighty orchestra.” He premiered The Imposter with the Nashville Symphony Orchestra in 2011 and has since performed it more than 40 times and recorded it for Deutsche Grammophon, which is a phenomenally impressive uptake for any new orchestral score.

Could anyone else play the solo part? Fleck ponders the question for a moment.

“I can think of three people who could. One of them is Noam Pikelny” — banjo player with Punch Brothers, new bar-raisers in the bluegrass world — “but honestly? Noam needs to differentiate himself from me. And here’s the point: anyone who is good enough to play this concerto should be writing their own concerto.”

It’s quite a statement, and one that places Fleck within a bygone tradition of composer-virtuosos. Maybe those forenames were auspicious after all.

Bela Fleck plays The Imposter: Concerto for Banjo and Orchestra with the BBC Scottish Symphony Orchestra at City Halls, Glasgow, on Saturday, January 23. He also performs a duo concert with his wife Abigail Washburn at The Old Fruitmarket, Glasgow, on January 24. Both are part of Celtic Connections, which runs until January 31