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As far as rock'n'roll takeovers go they don't come any tougher than replacing Ozzy Osbourne as the frontman of Black Sabbath.
In 1979 Ronnie James Dio took up the challenge when Ozzy was asked to leave the band following constant in-fighting and issues surrounding his extravagant drug taking.
It has to be said, the mythical Sabbath period of the early 70s, with albums like their self-titled debut and the brain- and bone-crushing heavy metal classic Paranoid can never be matched.
However, when Dio took over as singer he revitalised what had become a ramshackle and wary sounding Sabbath by the end of the 70s.
With his flamboyant antics and powerful voice that was more classic sounding than Ozzy's demented and creepy shriek, the band's next album, Heaven and Hell, from 1980, was equal in popularity to many of the band's early classic albums.
"It was a lot more melodic and smoother in style - something eatable from beginning to end," he says, describing the new Sabbath sound they had come up with.
That early 80s line-up, featuring Sabbath founders Tony Iommi on guitar and Geezer Butler on bass, along with Dio and drummer Vinny Appice, are touring as Heaven and Hell and play Auckland's Logan Campbell Centre on August 16.
The concert will feature songs from the albums Heaven and Hell, Mob Rules (1981) and Dehumanizer (1992), all of which featured Dio, as well as three new songs, including an epic beast called The Devil Cried from the new Sabbath compilation The Dio Years.
Stepping into Ozzy's shoes wasn't a big deal for Dio. Before Sabbath he was in Rainbow with guitarist Ritchie Blackmore, the founder of Deep Purple and renowned perfectionist.
"There really is no harder job than that," he chuckles.
Iommi and Dio talked on the phone about collaborating even before Ozzy had left the band and a short time after that conversation they met in Los Angeles, went into the band's rehearsal space - "Ozzy wasn't there; he wasn't interested at that point" - and wrote Children of the Sea from Heaven and Hell.
"I think at that particular time Tony wanted to be more adventurous and wasn't very happy with the production and the [song]writing of the band. But musically the way that I think and luckily the way Tony wanted to think was much more orchestral in scope than it ever was before.
"And," he adds wryly, "Tony wasn't very happy with the things that had gone on with Ozzy, more than anything. I'm not here to tell tales though."
Dio's hardest job during this time was convincing loyal Sabbath fans that he had what it took to front their beloved band.
"I remember getting the finger for about the first month. Then it just suddenly stopped and I was accepted. So they [the fans] either went away or liked what we were doing and were converted."
He says with the release of Heaven and Hell, and the subsequent tour, many new Sabbath fans were recruited. It was on this tour that Dio popularised "the goat", the one-handed symbol - done by extending your index and little finger while holding the middle two down - that is synonymous with heavy metal to this day.
So while Ozzy may have bitten a bat, Dio gave the world the goat.
He refuses to take credit for inventing the symbol and explains that it was a sign he got from his Italian grandmother who used it to "ward off the Evil Eye or to give the Evil Eye". He says he simply started doing it because it suited Sabbath's sound.
"I'm a pretty expressive person anyway and so I just decided to let my expressiveness go and I become this person on stage who listens to the music that he's singing and hearing and I try to interpret it with genuine gestures all of the time. They have to be genuine, you can't just go, 'Oh, I know, I'll put my hand in the air'. It's all in what happens emotionally."
Dio's first stint in Black Sabbath lasted only three years, then there was a brief reunion in 1992, and now they're back together - for a time at least - as Heaven and Hell.
He admits that musically they don't always see eye to eye but his partings in the past were "never personal ones like, 'I don't like you'."
"It's a joy to play with these guys again because the band is just absolutely unbelievable. It gets better every night. And personally it's been satisfying - they've always been great people and always will be. It makes this time of life worthwhile."
Dio says the thing that makes Iommi such a unique guitarist is the size of the sound he produces.
"Once he got the sound he wanted, those giant hands of his manhandle the guitar in the way he wants it to. He's in charge of his instrument and that's the most important thing about Tony."
He's not scared to give himself a big pat on the back either.
"I'm good at what I do. I'm a good singer and I've influenced a lot of people. I believe in the music that I made and the music that I'm going to make and I've always had the talent to do this."
And the reason he has been involved in "heavy music" for nearly 40 years?
"I've played with a lot of bands at a lot of different times, be it Sabbath, Dio, or Rainbow, and that is what heaviness is supposed to be. I just like the strength of it."
Lowdown
Who: Heaven and Hell (aka Black Sabbath)
Line-up: Ronnie James Dio (vocals); Tony Iommi (guitar); Geezer Butler (bass); and Vinny Appice (drums)
Where & when: Logan Campbell Centre, Greenlane, Auckland, August 16 (with special guests Down)
Latest album: The Dio Years, out now
Essential albums: With Dio, Heaven and Hell (1980), Mob Rules (1981); with Ozzy Osbourne, Black Sabbath (1970); Paranoid (1970); Master of Reality (1971); Black Sabbath, Vol. 4 (1972); Sabbath Bloody Sabbath (1973).
