Mrs La Grouw said in 2011 an Australian won, otherwise it had always been a New Zealander.
She said the prize for the winner was $20,000, with $10,000 cash, $5000 towards costs to enter the Sydney Aria competition and $5000 towards tuition or audition costs.
The full Auckland Philharmonia Orchestra will back the finalists, which Mrs La Grouw said always lifted the quality of singing.
Mrs La Grouw said it was really great to have a full, professional orchestra performing in Rotorua.
The guest artist for the evening is Simon O'Neill who travels all over the world singing, she said.
She said Mr O'Neill had links to Rotorua, as he married a woman from here.
The event has attracted top singers in the past, with last year's winner being Amitai Pati from the popular classical trio Sol3 Mio.
"It truly is a world-class event. I've been to operas all over the world and I think we have the best singers. The New Zealand singers are phenomenal."
She said all the finalists would go on to have a professional singing career, so it meant a lot to the people who entered and got into the finals and was good for their CVs.
The public were welcome to come along to the heats on Friday and Saturday for a gold coin donation, and the finals night on Sunday was full ticket price, she said.
Tickets are available from www.ticketmaster.co.nz.