Singer George Donaldson, 46, died after a heart attack in March leaving the male singing group without one of its founding members.

Four of the group were in Sydney on Thursday before the start of their Australian tour and agreed that continuing with their dates Down Under was the best thing they could do.

"It has been a difficult time but there's strength in numbers and this tour has been all about celebrating the man who was an incredible guy to be around and made a massive impact to all of us," singer Colm Keegan says.

"One thing that's said about groups on tour is that you're not colleagues, you're family.

"The last few months have been incredibly difficult for all of us. But the one thing we wanted to do on this tour was pay homage to one of our family, George."

The other three Irish men, Neil Byrne, Keith Harkin and Emmet Cahill, agree their upcoming tour is one of the best ways they could celebrate Donaldson's life.

"It's not easy but as the old saying goes: the show must go on," Harkin says.

"And I know if George was in this situation he would be exactly the same."

The four men display an easy charm when they're together; it's not hard to see how they win audiences everywhere. This will be Celtic Thunder's third trip to Australia after enjoying impressive sales worldwide.

Their 2012 DVD The Show was on top of the ARIA charts for 33 weeks with the group selling two million albums worldwide and more than 700,000 concert tickets. The Celtic Thunder YouTube channel, Thunder Tube, has also clocked up more than 28 million views since 2008. "Australia is a massive part of the Celtic Thunder chapter," Keegan says.

Keith Harkin, a long-haired surfer, particularly likes visiting Australia at this time of year as the "winter swells are coming in".

Harkin says performing in front of family gave him more of a thrill than when the group sang at the White House for US President Barack Obama.

"I had the pleasure of playing in front of my grandmother and my mummy in Radio City [Music Hall] in New York so it's pretty spectacular ... but President Obama was definitely very cool as well," he said.

WIN Entertainment Centre, May 28

AAP