In contemplating the return season of the Melbourne Theatre Company’s musical adaptation of Miles Franklin’s novel My Brilliant Career, the show that has defined her own career thus far, Kala Gare felt that forewarned was forearmed.

“Knowing the load was so helpful,” the singer and actor says. “The life outside the role is quite minimal. You spend your one day off recovering and preparing for the next performance. But I’m hoping this time I can carve out a little bit more space for myself.”

It’s a sentiment that neatly underlines the key theme of both the novel and this musical, which was universally acclaimed when it premiered in Melbourne last year and is now back in the city before touring to Sydney, Canberra and Wollongong. Gare inhabits the central role of Sybylla Melvyn – a part played indelibly by a young Judy Davis in Gillian Armstrong’s 1979 film – the headstrong eldest daughter of a dissolute drunk who refuses to be constrained by her circumstances, in a performance of astonishing range and power. While Gare claims it’s an ensemble piece, it’s also clearly a star vehicle.

“I was given a lot of freedom,” Gare says of the role’s genesis. “I remember one moment, when Anne-Louise [Sarks, the director] said to me, ‘You wanted to cartwheel then, didn’t you?’ And I said, ‘I did!’ And now that cartwheel is in the show.”

While the company did employ understudies and swings – cast members who can play multiple roles in a season – in its initial run, this time they’re more fully integrated into the production.

“It gives us a level of support that’s really comforting,” Gare says. “You bring your unique self to the character and then when someone else does it, they bring their unique self to the character. Mel [Bird, who plays various roles but also understudies Gare] is stunning. She will be a brilliant Sybylla, I have no doubt.”

Finding the right cast – 10 actor/musicians who perform the score live on instruments (some strapped to their bodies) – was a task that largely fell to musical director Victoria Falconer, who cut her teeth on the actor/musician-led musical Once and has become a leading expert on the form.

“There is a very specific kind of human that can do it,” Falconer says. “There are songs where someone is singing with one type of phrasing, playing an entirely different type of phrasing on their instrument and then dancing, so their feet are doing something different again! Cross rhythms like there’s no tomorrow.”

It sounds fiendish, but the result is a sonic cohesion and dramatic synthesis you rarely get in a traditional play, a sense of communal force. “You are seeing people operate at the zenith of their creativity,” Falconer says. “They’re doing the most, and that’s so impressive. Actor/muso shows don’t always work, but when they do …” Falconer drops her voice to a whisper, “… it’s amazing.”

Composer Matthew Frank – who developed the piece with longtime collaborator Dean Bryant and playwright Sheridan Harbridge – has crafted a “mix-tape” score that ranges from pub rock to bush folk by way of the traditional musical theatre ballad, full of syncopation and jangling rhythmic structures. But it’s also designed to be “playable”, says Falconer: “It has to be manageable enough for the people to run around and also give us a full and nuanced character.”

For Sarks – who, like Gare and Falconer, came on to the project early and helped shape it into a living, breathing organism – My Brilliant Career demonstrated its potential from the beginning. “I remember saying to the team, ‘The way you tell this story, the energy in this space, the generosity of it – if we can capture that in a theatre, then something very special is happening’,” she says.

The kinetic energy generated on stage – evident from the moment the audience enters the space, as the band rouses to life on Marg Horwell’s gorgeous wheatbelt set – is deliberate but also a function of this particular ensemble. “I think you can feel process in a final show, and this process was very playful and organic, and sometimes a little bit mad,” Sarks says.

My Brilliant Career was always a novel of searing feminist thought, but this creative team seems to have unlocked something deeper and more open-ended in the work. For Gare, Sybylla moves from “a very black-and-white view of the world at the beginning to a realisation that everyone else’s story has value, that everyone is just as complicated as she is”.

Sybylla’s maturation isn’t simply about self-actualisation in the “girl power” mode; it’s also about humility and self-sacrifice. This suits Sarks, who prefers her feminism “to be complex and difficult, actually. To be questioning itself as it’s unfolding. Ultimately, if feminism is to succeed, it is in a deeper recognition of the humanity in each other.”’

There is also a lesson for the nation at the heart of this musical that Miles Franklin probably couldn’t have conceived, a kind of offer or challenge. Sybylla sees the possibility not just of a freer future but one that accepts responsibility, what Sarks calls “a gift, but in service to something bigger than herself”.

“Sybylla’s so fearless,” Gare says. “Playing that eight times a week, it does seep into the soul. Show up scared, show up without the answers, but show up. I feel like she’s given me enormous courage.”

• My Brilliant Career is on at MTC’s Southbank Theatre until 23 February, then Canberra Theatre 7-15 March, Sydney Theatre Company’s Roslyn Packer Theatre 21 March – 26 April, and Illawarra Performing Arts Centre, Wollongong 8-17 May