The company will be putting on a free performance of the 174-year-old Giselle in front of what is expected to be a large crowd.

"I think ballet's one of those artforms that people can think of as being very elitist. But in fact our audience is from a really broad demographic," artistic director David McAllister said.

Mr McAllister described the core group of ballet supporters as "mainly female, 50-plus and well educated", but said it was important to attract others.

"There is more of a youthful audience coming through. What we've found is we tend to lose our audience between 28 - when they're finishing their university - through to about 45," he said.

"We tend to lose that middle group because everyone has family, children and other commitments. We've got this life cycle. So one of these sorts of events is about maintaining that life cycle."

The company is hoping the free concert will entice crowds to attend its production of Cinderella next February.

The Australian Ballet describes Giselle as a "tragic story of love, madness and betrayal" featuring a village girl who needs to dance with her lover in a forest haunted by ghosts of jilted women.

Mr McAllister said an outdoor setting required some tweaks to the show - they are using a backing track instead of a live orchestra and some other stage props aren't practical.

"That ambience of nature is quite beautiful…when you get a gust of wind there's that whole movement that happens that doesn't happen in a theatre," he said.

However there's also an element of unpredictability, Mr McAllister said. During a Darwin performance about a decade ago a kookaburra flew across the stage in Darwin while carrying a live, screeching rodent.

Gates for Friday's 7pm show, sponsored by Telstra, open at 4pm.