Interview: Phil Cunningham

"If you say 'Mormons' to me now, I think of all those clean-cut young men who used to come to our house – the missionaries from America with their Bazooka Joe bubble-gum and their comics with adverts on the back for monkey-fish. To a five-year-old boy, these guys were very exotic," he says.

We're in an Edinburgh cafe, just round the corner from Cunningham's old Mormon church. Sheepishly, I admit to having frequented the building when it worshipped the body beautiful as a health club. But Cunningham says he didn't last long as a Mormon and the church's disapproval of tea was not the only reason.

"I had a very religious childhood: scripture study every morning, church four times a week, playing the organ in Sunday school. I even helped build a new Mormon centre in Edinburgh. I dropped some bricks on a just-laid drain and smashed it.

"But the rules and regulations of the church marked you down as odd. At a self-conscious age, I'd be the only boy on a school outing to the zoo without a thermos full of tea because the church didn't want you getting addicted to anything. Pity I had a hipflask in my bag as well."

He's joking, I think, but at 15 Cunningham was to turn his back on the Mormons. He grew his hair, got his first earring and began the addiction to folk music that has sustained a 32-year career as performer, composer, producer, broadcaster, academic and all-round champion of the craft. For Cunningham there was nothing fey about folk, and his band Silly Wizard intimidated the 1970s punk rockers supposedly terrorising the land. "We were wild for the drink and quite a few punks admitted they couldn't hold a candle to us," he says. "One night in Liverpool when we were all still relatively sober we presented Johnny Rotten with an album for his birthday; Silly Wizard were one of his favourite bands."

In recounting these excesses, Cunningham is not bragging about the distance he's travelled from the long-gone church round the corner. "I have a lot of respect for the Mormons. And my respect for anyone with a faith borders on envy. It must be wonderful to believe. I can't call myself religious; if anything I'm a spiritualist. But as you get older – and I'm 49 tomorrow – you get more curious…"

That curiosity has just gone into overdrive. His new telly series for BBC Scotland is a history of our religious music and making it blew his mind. The stars of Grace Notes include St Columba, who gave us some of that sixth century religion, the Hampden Park-filling American evangelist Billy Graham and the Renaissance composer-monk Robert Carver, who Cunningham hails as "our first musical celebrity".

In the two programmes Cunningham listens intently to an early chant protesting at "English incursion" to Scotland. He's shocked to learn of the Covenanters tied to posts in the Solway Firth who refused to recant their beliefs and kept on singing as they drowned. The Reformation silenced Catholic masses for being decadent and Cunningham chronicles the periods when the sound emanating from our churches was "reliably dreich", when the book of approved tunes numbered just 12, and when Bruch, Haydn and Beethoven admired our religious music far more than we did. Its suppression at various times, he says, has been "nothing short of a tragedy".

Grace Notes is a kind of follow-up to the much-admired Scotland's Music. For that series Cunningham was on home ground, although he says his approach to making musical documentaries is always the same: "Just because I've been a musician for 32 years doesn't mean I've been paying attention."

This one certainly got him thinking. "Every night after filming, I'd ask myself: 'Am I still flat out anti the whole religious thing, or is there part of me that might one day tip back?'" The debate, he adds, is ongoing.

"I'm not finished learning about our church music. In my ignorance I didn't know about the Covenanters. There wasn't much Scottish history taught in my school. It was all Henry VIII and Good Queen Bess."

Cunningham's alma mater was Portobello High where the music teacher dismissed him as "a waster who was going nowhere". He says he didn't resent this, but for a while the school would receive postcards signed "Cheers, Phil" from his far-flung travels with folk music. For Grace Notes, he visited Nashville, Lower Saxony and Inchcolm Island in the Forth – the Iona of the east – near the home in South Queensferry he shares with his partner Annie and their two dogs.

Cunningham is a big man in every sense. A giant of the folk scene, he's probably best known along with ace fiddler Aly Bain, folk's other CEO, for the Hogmanay double-act on Beeb Scotland. Playing so fast that only dogs can hear them, they seem like the only sober men in the land as another year lurches in. But he doesn't want to be quite as big by the end of this one so has set himself a target – with his birthday marking the start of a delayed resolution – to lose weight and generally live more healthily. That's no mean feat in this profession when you love the bonhomie as much as Cunningham.

"I like to joke that it was the ban on black pudding which finished me and the Mormons," he says. "I couldn't imagine that in the 1970s God was on the blower to the church to get Scots to stop eating blood products – not when the Irish Troubles were at their height.

"But when I was 16 and I followed my older brother Johnny into the band I was living in a squat in Liverpool – so after school and after the Mormons, my life had no rules. Suddenly I was smoking for Scotland. I gave up 11 days before my first heart attack, aged 37. I had another one at 38 and doctors told us it was probably genetic but Johnny didn't heed the warnings. He had a heart attack at 46 and died."

Grace Notes contains intriguing morsels of Cunningham's own story and the part played in it by religion. We learn that his father was one of Scotland's last Temperance Kings, an honour bestowed on boys aware of the perils of the demon drink despite the tenderness of their years. Maybe he's saving the rest of the tale for his autobiography, currently in production, but he admits: "It's funny me talking about religion because I'm my father's son and he always said you should never discuss it because it only causes trouble.

"When he died of cancer I became vaguely interested in Buddhism. But that was me being the master of misdirection as usual. I think I can overcome anything by kidding myself it's not actually happening. Johnny's death tore my mother apart but her faith got her through it and because of that I would never criticise the Mormons or anyone who believes. But I am anti-denominational and anti the attitude that you have to be a certain kind of Christian, that one kind of religion is far superior to anything else."

It is, however, impossible to be all things to all people and to please everyone. Cunningham may not know this as a devout churchman, but he's been musical director of the Hogmanay hootenanay for 18 years and some would contend that's one of the toughest jobs in TV.

The critics seem to store up their bitterest barbs for Auld Year's Night, as Jackie Bird can testify after the Hogmanay where she fell out of her dress. "I've had some right slaggings too," says Cunningham, "and I can remember the worst of them word for word: 'The formerly staid beaky accordionist swept on stage in a wishy-washy panto jacket and leather trousers – a sure sign he's bonking a woman 20 years his junior.'

"Tragically, I wasn't."

Grace Notes starts February 14 on BBC2 at 8pm