As is the wont of rock stars who prefer not to meet their public every time they fancy a drink, Ritchie Blackmore has a bar in the basement of his home in Long Island. When you walk in, he says, you would notice that it has “that vibe of being haunted”.

In the bar is a clock, a gift from a friend. And that clock, Blackmore says, contains a ghost. “It only chimes when it’s in agreement with something, or when we’re talking on a frequency the clock understands,” he says, solemnly. “It’s a very strange thing. And if we ever talk about religious things, it gets excited and it starts going off.”

Mind you, he says, that’s not surprising, really. He has noticed on those TV haunting shows that a disproportionate number of ghosts are attracted to religious people and religious symbols. “I don’t know if that taunts the ghost, or sets off an energy that excites them. I was watching a show last night, and they were investigating this house and sure enough there were crucifixes and religious pictures all over the place. It’s strange they hadn’t figured that one out and thought it might have been causing ghostly activity. I find it a fascinating subject, because we’re all going to end up going somewhere and it would be nice to know if it was a nice place.”

Blackmore is one of English rock’s great eccentrics. Not in a cuddly, tea-party sort of way, but in a faintly malevolent, unpredictable and quick-to-anger sort of way. In both Deep Purple and Rainbow, a lineup of which he has convened for a summer amble around the UK’s arenas, he developed a reputation for volatility, and that volatility was accepted because he also had a reputation as one of hard rock’s most electrifying guitarists – he was, after all, the man who wrote rock’s most recognisable riff, Smoke on the Water.

Then, in 1997, he cast rock behind him and, with his wife Candice Night, started playing medieval and Renaissance music – in some version of period costume – under the name Blackmore’s Night. What he wanted, he says, was “to be a wandering minstrel and play to 10 people a night”, and to be able to stay in castles when he toured. And that’s precisely what he did for the next 20 years or so, until the Rainbow name was revived last summer.

Ritchie Blackmore (far right) and his wife, Candice Night (far left) in Blackmore’s Night in 2006. Photograph: Peter Bischoff/Getty Images

One positive of Blackmore’s Night was that he did not have to put up with the whims of people such as Graham Bonnet, who sang on Rainbow’s hits Since You Been Gone and All Night Long, and once had the temerity to want to have his hair cut short. “We were a long-hair band,” Blackmore says. “In 79, everybody wore denim and had straggly hair. But he looked like a Las Vegas casino man. He had such a great voice, we thought: ‘Oh, it doesn’t matter. We’ll rough him up a bit round the edges.’ But he never took to that.” Three months before Rainbow’s first UK gig with Bonnet – he was the second in a revolving door of singers – Blackmore demanded he refrain from having his hair cut. And then gig day arrived.

“We had a roadie guarding his dressing room, to stop him getting out, because he was threatening to have his hair cut. It was very petty, but it had become an obsession with me. But he got out of the back window and went and got his hair cut. I didn’t see him until we went on stage, and, sure enough, he’d had his hair cut really short. He was doing it just to annoy me.”

Graham Bonnet, with short hair, in Rainbow, 1980. Photograph: Shinko Music/Getty Images

Blackmore was seized by rage, and the desire to stove in Bonnet’s head with his guitar. On stage. In Newcastle. In front of several thousand people. He managed to restrain himself, which is not as obvious a conclusion as it might be for other people. “It’s the principle,” Blackmore says. “I took it as an insult. I don’t think I spoke to him again after that.”

Three things are certain in heavy rock: death, taxes, and that you will part ways with Ritchie Blackmore. In Rainbow alone, he has been through 26 musicians. Why?

“I’ve been told it’s because I don’t pay anybody. I don’t see why that should make a difference. If you’re into music, you should do it for nothing. In fact, that’s the way the music business is going, isn’t it? I thought artists were expected to play for nothing.”

That really doesn’t make being a globe-straddling, internationally successful band sound like much fun.

“I try not to have fun. I work very hard at not having fun.”

Why on earth would he do that?

“I don’t think the world is a fun place. I’m very content in my own mind, in a way, but fun, I’m not too sure about. I don’t quite know what fun is. I don’t know why I should walk around with a perpetual grin on my face, saying everything’s wonderful.

“I just don’t fit into the ‘fun’ area,” he continues. “A lot of musicians go: ‘Oh, that was fun.’ Well, I like to think that music is very serious, and it’s not fun. I’m not one of these guys that likes jamming with people and having fun; music is too serious, and I don’t feel like I can relate if I’m having fun. It’s hard work and it’s really gratifying to do, but fun? Fun is something where someone tells a joke and they laugh for 10 seconds. Music’s much deeper than that.”

Blackmore (right) with Ian Gillan in Deep Purple, Tokyo, 1985. Photograph: Shinko Music/Getty Images

His greatest derision has often been reserved for Ian Gillan, his former bandmate in Deep Purple. There is a documentary about Blackmore in which he spends a large chunk of the 90 minutes deriding Gillan, but today he is genuinely conciliatory. Yes, he talks about a fight the pair had in Cleveland, Ohio, during which Gillan ruined Blackmore’s dinner by pouring ketchup over it, prompting Blackmore to throw it in Gillan’s face. And he talks about deliberately provoking Gillan by playing the song Child in Time on stage when Gillan had requested it be left out (it requires the singer to hit a large number of very high notes). But then he also talks about boating on the Thames with Gillan and their then-wives. “I got caught up in the reeds and the branches and the roots of this tree that went out into the water. And now, I was stuck on the Thames: I couldn’t go anywhere. And Ian was so brave: he just went underwater and he pulled the whole boat – it was a six-berth boat – pulled the whole boat out from the branches, and I was free. He didn’t need to have done that.”

Blackmore met Night at a football match he was playing in; the story goes that he sent a roadie to get her name and phone number. Why not ask himself?

“A fear of rejection,” he says.

What? After decades in huge bands, wielding incredible control with utter ruthlessness, he was afraid of rejection?

“I think we all are. It pushes you on: if you think you’re going to be rejected, you try harder. I think it all goes back to schooldays, to not being a good pupil. My father was pretty stern, and he was very educated, so I didn’t quite fit the mould; he didn’t know what the hell I was doing. That stayed with me for quite a while, probably still does.”

That’s the father who bought Blackmore his first guitar, and handed it to him with the words: “If you don’t learn this properly, I’m going to put it across your head.” Which might be where the idea for smashing in Bonnet’s head came from.

Blackmore likes the fact that people think of him as rock’s angriest man – “It keeps the people I don’t like away” – but there are signs that, in his 70s, he is at last mellowing. He “bears no malice” to Deep Purple now, and would play with them again if he were asked (“It’s probably not probable, though”). But, I suspect, it’s still unwise to have too much fun around him.

• Ritchie Blackmore’s Rainbow play four UK arena shows in June, including headlining the Stone Free festival at The 02 in London on 17 June.