“Well, we are all very different, individual. Máiréad [Carlin] plays the fiddle and the three of us who sing differ in our vocal styles completely… David Downes, who created Celtic Woman, directs to allow us our individuality.”

As McFadden warms to her subject, she thinks of another great Irish characteristic – “we don’t shut up”.

The sister of former “Australia’s Got Talent” judge Brian McFadden, Susan is better known in Dublin and London (where she lived for eight years) as the star of American musicals. In fact, she was playing Elle in “Legally Blonde” when she got a call from Celtic Woman.

“I was always playing a character in the Broadway musicals and this was the first time that I could be myself.”

She’ll be here on September 19 with her co-stars and an equally Celtic ensemble that includes a band, bagpipers, Irish dancers and the Celtic Tenors.

Her mum comes from a very musical family in Tipperary and is one of 11 siblings. Her dad comes from Donegal and is one of 12.

“When one person starts singing, the rest follow on; we’re singing all the time,” she says.

“My aunty’s favourite song was ‘Caledonia’ and lo and behold, my solo is the very same song, so I rang aunty and said: ‘You’ll never guess what I’m singing’, and she came to see me in Dublin.”

Naturally, there’ll be some famous pieces such as “Danny Boy”, which people love to hear because they feel it’s typically Irish, Celtic and traditional. Purists may point out that it’s actually quite a modern song, but no matter, it’s the perception that counts and she’s sure that it’s one that will move audiences.

Another modern one is “You Raise Me Up” – “always very stirring” – and the song “Téir Abhaile Riú”, which roughly means “The Home”. This is always performed interactively by the singers and sees McFadden sitting on the lap of an audience member.

“There’s a bit of banter and a bit of craic in the show… I pick the person who looks like they’re up for it,” she says.

While the theatricality of the show, full of magical dancing and lighting effects, is justly praised, it is really the music that counts.

Celtic Woman 10th Anniversary World Tour, Royal Theatre on Saturday, September 19, bookings to ticketek.com.au