With 40 years of high-profile acting credits to her name, Sigrid Thornton is Australian showbiz royalty. But resting on her laurels clearly has zero appeal. Instead, she is always on the look out for roles that will challenge her and teach her something new.

Take the new Australian production of Fiddler on the Roof in which she plays Golde, the wife of Tevye (played by Anthony Warlow) the milkman with five daughters who tries to hold onto tradition in a changing world.

Directed by Roger Hodgman, the production opened in Melbourne at the end of last year and has its official Sydney opening tonight.

“It’s my second musical. I have to laugh because I never imagined that I would ever work in musical theatre but it started with A Little Night Music (for Opera Australia in 2009, also with Warlow). And I love it, I absolutely love it,” says Thornton.

“There’s something about having (a score). This is really from Anthony’s mouth so I’ll quote him in saying that it’s a soundtrack for your performance – because that is exactly what happens. Having musical accompaniment, working with an orchestra and actually singing some of your emotions is very exciting. I’m on a huge learning curve. I’m surrounded by people who have been doing it for a very long time and that is an attraction.”

This time around Thornton decided to take singing lessons before going into rehearsals.

“That was an attraction for me, a genuine pull. I said ‘if I’m going to tackle this at all I wanted to improve my singing voice,’” she says brightly.

“Now, I’m not in the job to sing like Anthony or indeed any of the other singers in the show but having said that I fancy that my voice has definitely strengthened during the course of the run. I always wanted to be able to pull off a song better, simply for my own pleasure. I never imagined I’d be able to put it to professional use but it’s been a gift.

“It’s always a gift to keep learning. It sounds terrifically corny but that’s why I’m still doing what I do. I like to keep stretching it out and discovering what I can and can’t achieve. You are always discovering the limitations and boundaries of your skills but you want to try and extend those as much as possible,” she says.

Thornton has a small, light singing voice, it must be said, but she creates a strong, believable character as Golde.

Set in 1905 in a small Jewish village in Tzarist Russia, which the inhabitants are forced to leave at the end of the show, Fiddler on the Roof is a musical theatre classic with a much-loved score including songs such as If I Were a Rich Man, Tradition, Matchmaker and Sunrise Sunset.

“It’s about a marginalised people but fundamentally it’s about love and family and community and connection and so they’re universal themes. Despite the fact that the show has been around a long time, the refugee thing is more current now than ever,” says Thornton.

Prior to rehearsals, Thornton knew the show “to the extent that a musical tourist would know it. I’d seen the film many years ago and I’d seen Topol (playing Tevye on stage) maybe 11 or 12 years ago,” she says.

“This is a very different production. One of the major differences is that it is a new orchestration. The most recent London production negotiated to do a new orchestration, which is a very complex thing as you can imagine, and so we were able to ride with that and it’s very beautiful. It’s much simpler, much more folky and it’s probably more true to the music culture of the day.”

With her children now grown-up, Thornton has been able to take on plenty of work in recent years.

“I’ve always been a career mother but I actually have had long periods away from work for reasons of family. But the kids are now 24 and 30 so they are adults,” she says.

She has certainly been busy. Last year, she received accolades for her performance as Judy Garland in the Channel Seven miniseries Peter Allen: Not the Boy Next Door. She has joined the cast of Wentworth, Foxtel’s contemporary re-imagining of Prisoner, playing a cosmetic executive accused of murder.

“I have the honour and privilege apparently of being the only original Prisoner cast member to appear on Wentworth,” she says.

She also has a role as a cyber-security executive in the second series of the ABC’s acclaimed political drama The Code and features in the Cairnes Brothers’ much anticipated second feature Scare Campaign.

“It’s actually been quite a roller-coaster year now that I think about it,” she says of the past 12 months or so.

“That was another attraction to Fiddler – to play a serious character role in something that was a different medium because I’ve done quite a lot of films and television recently. That’s been really exciting but I wanted to try something completely different as Monty Python would say.”

Now 57, Thornton says she needs “to explore what’s out there for women my sort of age. There are still limitations for women but I think the gap will gradually close on that score. I think it’s really interesting looking at what’s coming out of the States. I was browsing through Variety the other day (and looking at) the pilots that are being made in the States and the majority seemed female driven and I was quite interested to see that.

“I’m an optimistic type. That’s my personality. I think in general equality and opportunity for the sexes (in Australia) has still got a fair way to go for a country that’s highly developed in all sort of ways. But it is changing and it’s changing for the better.”

Fiddler on the Roof plays at the Capitol Theatre, March 24 – May 6. Bookings: Ticketmaster 136 100

 A version of this story ran in the Sunday Telegraph on March 20