New Nazareth singer Linton Osborne has hailed Dan McCafferty as a “class act” after the retired vocalist helped his replacement through the ordeal of his first show.

Osborne was given the job in February, months after the original frontman was forced to quit three songs into a gig in Switzerland, leaving his bandmates fearing that their careers were over.

But with McCafferty's blessing, Nazareth powered on and hired their second-ever vocalist, who was previously a club singer – and once regularly dressed as a vampire Elvis character in a previous band.

He made his first appearance with the Scots veterans last month in Inverness. Just before he went on his predecessor left a message on his phone.

Osborne, who's known Naz for years, says: “I've still got the message. How much nicer can a man get? There's no way he would have wanted to give this job up. Not a chance. But he obviously had to, and he did it with such class.

“Dan and I had some great conversations over the years, but never in my wildest dreams did I think I'd be doing his job. The hardest part hasn't been learning the songs, it's learning every wee phrase. But our drummer Lee Agnew was fantastic; he's got a great ear."

Once he'd started there was no stopping him. “When you're in the zone you don't really think about anything else – you just want to enjoy yourself," he says. "There's something about rock 'n' roll, something it does to you. It sends a wave right through the bottom of your feet and out the top of your head and you just think, 'This is great'. You never want it to end.”

McCafferty's retirement means bassist Pete Agnew is the sole remaining founder member. He says: “We didn't do auditions – we had friends in to see if they fitted. We had people writing for the job from Russia, America, Canada. We even had people from Brazil, which was really handy… just nip over for a gig in Bournemouth and back up the road!

"Linton pointed out he was available. I'd seen him sing and knew he was good. Right from the start he knew our songs anyway because he was a bit of a fan. It was perfect.”

In the weeks after the dramatic events in Switzerland last year, Naz wrestled with the choice of quitting or going on without their iconic frontman. In the end, the decision was taken to keep going and to promote the upcoming album Rock 'N' Roll Telephone, which was recorded before McCafferty's departure, and features his vocals.

Agnew says: “When Dan said he wasn't going to be doing it any more, we sat there for the first month thinking, 'What are we going to do – are we going to continue?' It's like if Mick Jagger leaves the Stones. I can tell you if Keith Richards leaves, it wouldn't matter. You can always get an instrumentalist that can be exactly like the guy who left; but you can't imitate a singer. It was Dan himself who said he wanted the band to continue because it's been his whole life."

Osborne's second and third gigs took place in Russia, the furthest his career has ever taken him. But he feels the transition from club singer to rock frontman has gone smoothly. He says: “I've been singing in bands since I was 16. I kept playing in bands but there wasn't enough money in it, so I went on the cabaret circuit – pubs, clubs and holiday parks or whatever.

“I was in a band called The Monsters Of Rock and we played Classic Rock – AC/DC and Zeppelin – dressed as monsters. I was The Count, a vampire Elvis type character. We had Animal from the Muppets on drums and the Grim Reaper on bass. Frank Pagenstein who did all the Zeppelin lead guitar and a friend of mine who played Angus Young's stuff, who called himself Angus Auld. He was only 18 at the time – that was the irony of it.”

Like any band that goes through line-up changes, Naz have come in for flak from some quarters. Guitarist Jimmy Murrison was often a target for fans of original axeman Manny Charlton – but so far Osborne hasn't been a victim.

Agnew says: “Jimmy's had it for years, guys shouting up to him about Manny. That guy's been out the band for quarter of a century – are you kidding me? You still get it and it can be off putting. And for a singer it would be really annoying, but Linton's never got that.”

Osborne vows that if the backlash does eventually come, he'll be ready. He states: “I can handle it. I've got the best job in the world – I don't care. The guys hardened me to it already, the guys and Dan.

“I'm waiting for a phone call from Brian Johnston to sort of guide me through the process of it, because he must have got a bit of that as well. It worked out okay for him, and that's what I'm thinking. It's not like I've come in and undercut Dan and took his job. It's been a nice, welcoming handover.”

A tour of Canada to coincide with the release of Rock 'N' Roll Telephone starts in June, followed by more dates in Russia and a trip to Brazil.