Despite being an Aussie for 64 years I'm at a loss about ideas to post here too.
Words to add to the mix of questions are
When --- Now? During the settlements of the 19th century? During early settlement?
Where -- In the outback? In the urban areas? In reginal cities? On the goldfields?
In whose opinion -- Aussies? Historians? Song collectors? People outside Australia?
About what and whom -- which I think has been covered.
The answers could be as different as -- all the Stephen Foster songs, the songs of the various workers, songs of the folk revival, and rock and roll.
By the way if you go to Warren Fahey's site be sure to take a look at Billy Barlow. Now there's an influential singer -- several of him!!
Cheers, Joy