I don't know much about these guys but the Australian Museum site says they're in decline because of habitat loss, causing decrease in food supply and loss of breeding nest sites.
From the Birds in Backyards website, it says, "Yellow-tailed Black-Cockatoos have a long breeding season, which varies throughout their range. Both sexes construct the nest, which is a large tree hollow, lined with wood chips. The female alone incubates the eggs, while the male supplies her with food. Usually only one chick survives, and this will stay in the care of its parents for about six months."
Okay, so none of the sites say anything about their call being how I described it. Maybe it's my over-active imagination :)