I hoped to meet Frankie Valli when I flew to New York for the final audition for Jersey Boys, but he was far too busy gigging all over the place. Even in his seventies, Frankie’s still giving it large. We first came face to face last year when we shook hands at a photo call at the Prince Edward Theatre. I was so nervous. In fact we both checked each other out and I must admit that I thought, “Oh my god, I wonder if these guys really are hard core and still have connections to the Mob. What if I give a bad performance? I might end up in the trunk of a car!”

I soon discovered that Frankie Valli is a shy, quiet man with a lot of depth. He even gave me his mobile number and told me to call him during rehearsals if there was anything I needed to know about his life. I haven’t called. The kind of things I wondered about are really deep. I thought I might depress him!

I’ve always loved Frankie’s music. When I was growing up in Newcastle, my mum never stopped playing hits like “Sherry”, so when I first went through all the songs in the show I even knew rare ones, like “Opus 17 Don’t You Worry 'Bout Me”. But I wasn’t aware of what Frankie went through personally, which is revealed in Jersey Boys – his troubled marriage, one of his daughters dying of a drug overdose and another in an accident, how he had to do crappy gigs just to pay off a million dollar gambling debt run up by Tommy DeVito. Then there were the fights on the road. Yet Frankie always goes into a new situation with so much hope.

You can never do an impersonation of Frankie Valli. His vocals were angelic, but when he went for that falsetto he always liked to step on it – toughen it up with a rock edge. Compared to most other musicals, singing 27 songs in one evening as Frankie means I get through a huge spectrum of sound – from mid-range to low notes as well as top Es and Fs. Let’s face it, Frankie wasn’t messing about when he sang!

Fortunately, our singing coach is Katie Agresta, one of the best vocal trainers in the business. She came up with an ingenious way of keeping our voices strong by pulling our tongues with flannels and then making us do vowel exercises. It’s torture, but it works.

The thing I admire most about Frankie and the boys was how they stayed together so long, even with all the problems they had. It took eight years before they had a hit, which means they must have had a lot of belief in their music. They were all hot-blooded Italian geezers from the streets, not like today where you get little boybands with the prettiest faces you can find and squeaky clean backgrounds. These guys had been in prison. There’s a real tale to tell.

(Ryan Molloy was speaking to Roger Foss)

Jersey Boys opens on 18 March 2008 (previews from 28 February) at the West End’s Prince Edward Theatre. A version of this interview appears in the March issue of What’s On Stage magazine (formerly Theatregoer), which is out now in participating theatres. Click here to thumb through our online edition. And to guarantee your copy of future print editions - and also get all the benefits of our Theatregoers’ Club - click here to subscribe now!!