A fleet of double-hulled waka hourua is expected to be welcomed to the shores of Wellington Harbour tonight (Monday night NZ time) with kapa haka, song, and theatre, to open the New Zealand Festival.

The performance is inspired by the arrival of navigator and explorer Kupe to Aotearoa, and will feature more than 1000 kapa haka performers and a 250-strong choir.

They're welcoming the four waka hourua that have travelled from as far as Samoa to be part of the opening of the New Zealand Festival.

At the final rehearsal at the Pacific Island Presbyterian church hall in Newtown it was the first time 100 Wellington Community Choir and the Pasifika Community Choir members had sung together.

Choir director Helen Tupai said it had been a great opportunity for her community of Samoan, Tongan and Cook Island singers.

"It's not every day that you're in a choir that will be singing to 20,000 people."

Composer and performer Warren Maxwell has written all the music, including individual pieces for each of the waka hourua, and he said it was all coming together.

"It is a waka, and we're steering it, and it went in the right direction," Mr Maxwell said.

"We've got all the kapa haka practices happening all around the city ... choir practices, there's choreography, it's a real kind of hive of excitement.

"It's awesome."

Final kapa haka rehearsals have also been underway for 'Kupe Hautoa', the haka especially composed by Mana whenua Te atiawa Taranaki Whānui.

One of group making up the 1000-strong haka is Te Kōnohete, a kapa haka group drawn from Wellington government departments.

They have been put through their final paces with haka composer Kura Moeahu.

"It initially started with 100 people performing the haka and I just said 'well, why not 1000?'"

'Kupe Hautoa' will be performed by schools, kura kaupapa and community groups from Wellington, Hutt Valley, Porirua, and as far away as Wairarapa and Ōtaki.

"To see Māori, Pākehā, Asians, Pacific Islanders participating in this, that's what Wellington is about," Mr Moeahu said.