Above the noise of a Philadelphia bar, Latonia Moore took a call on her mobile last month. What was she doing, her agent wanted to know.  ''I said 'I'm out with my friends having some shots. What's up?''' says Moore.

The lead in Opera Australia's production of Aida had just dropped out. Was Moore free? The US soprano had six days to get organised, on a plane and down to Australia.

If the speed with which she walks and talks as we head down suburban Marrickville Road during a rehearsal break is any guide, such a race to Australia would not faze Moore. She is as exuberant as the bright yellow flowers on her one-shouldered top.
Moore is poised to step into the title role in Graeme Murphy's production following the withdrawal of Italian soprano Norma Fantini. Moore's operatic star is rising internationally, yet her manner is more earthy jazz singer - the musical form in which she initially trained - than imperious diva. ''Lat-ah-nia,'' she says as we meet. ''Kinda like lasagne.''

This is the second time this year Moore has stepped into the title role of Aida at short notice. She made her unplanned debut at New York's Metropolitan Opera in March with just over a day's notice when the principal took ill. Her debut was the final night of the production and broadcast nationally. The otherwise fearless Moore admits she had a rare bout of butterflies when she stepped out of the Met's wings.