It’s a role he’s dreamt of since seeing idol Jack Black in the movie while still in high school – but one he thought he’d never be capable of performing.
“It’s the most physically and vocally demanding role I’ve ever done,” Armstrong-Robley says.
“It was one of the roles I always wanted and then I grew up and realised the vocal range and how fit you have to be – I always thought I’d love to do it, but I never thought I could.
“I’ve lost 14kg – that’s how fit you have to be.”
A passionate Jack Black fan, Armstrong-Robley grew up singing Black’s material and counts a Tenacious D concert as among his most memorable experiences.
“It’s the only concert I’ve ever lined up for - I lined up for eight hours to be at the front of their mosh-pit.”
Armstrong-Robley said his fellow cast members were incredibly talented - singing, dancing and playing musical instruments as they form a band at the behest of Finn, who’s posing as a substitute music teacher at a prestigious school.
“The majority of the show is me and my class of 18 kids on stage.
“It’s a tough ask for a kid – they’re phenomenal.”
Redcliffe Musical Theatre President Madeleine Johns says the production is based on the movie, with the musical score by Andrew Lloyd Webber, and will have wide appeal.
“We thought it was going to be hard to find could sing, dance, act and play a musical instrument, but we were overwhelmed,” she says.