"We weren't sure if we wanted a roomful of people doing Nirvana so we decided to go with 'Kiwiana' instead."
Contestants can be either a solo vocalist with a guitar, or two people - one singing and one playing guitar.
"No doubt Dave Dobbyn will make an appearance, but hopefully there'll be some traditional Māori music in there as well, and a really nice variety of songs," Goodsir said.
"It's all acoustic, so that's another reason to stay away from the 90s, I think.
"Once the contest is done, everyone sticks around and it turns into a fun, open mic free-for-all for the next few hours."
The top three contestants go onto the Riverside Shindig on Sunday, January 23.
"At the Shindig they'll play in between the musical acts," Goodsir said.
"From there, the judges will give them third, second and first place.
"The prices are decent too. The winner gets $500, second place gets $300 and third gets $100. That's all thanks [to] Annette Main and the Whanganui River Market Trust."
Goodsir said the competition was won last year by local musician Bobbi Hutchinson, who performed a version of Poi E by Patea Maori Club.
She will be a judge this year, along with Geoff Horne and Kellie Thurston.
They will be paying particular attention to a contestant's vocal performance, as opposed to guitar playing ability, Goodsir said.
If you're interested in taking part, contact Rohan Goodsir at rohanoz@aol.com before November 15.
The contest is at Porridge Watson on November 25. The first act will take the stage at 7pm.