"We're going to do all of the expected classical music that you would hear at a coronation. We're going to be playing at the church before the ceremony and it will be a blend with palangi and Tongan traditional music."
The group is made up of a selection of musicians from various parts of New Zealand, including a few travelling from places they are currently based in -- Paris and China -- specifically for the performance.
They were in Auckland over the weekend for one more full rehearsal before travelling to Tonga on Monday.
Mr Fennell said they had put together a musical piece which the late King helped with and which would be played at the coronation also. The piece is called: Camarata Pasifika.
The ceremony is expected to run for two to three hours and the Kiwi orchestra will play at the beginning and throughout the ceremony, before traditional and formal Tongan procedures take place.
Dignitaries, members of parliament and officials from throughout the Pacific and abroad will be present over the next week as celebratory activities take place, including a Military Tattoo on the last day of events on July 7.
Tonga's new king, a lay preacher, is known for being conservative and deeply religious. His late brother was known for his eccentric and lavish lifestyle, often riding in British-styled black cabs.
Asked how he felt about performing for such an elite event, Mr Fennell revealed it would actually be the second time he would be playing at a Tongan coronation and regarded it as a huge privilege.
"Over my career, I've played for the Queen of England and at some pretty amazing places...But this one cuts the cake because I think the Tongans are wonderful.
"It's so regal and the warmth of the country and the people - you can feel that. You can feel the love from the Tongan people for their King."
Tongan Coronation:
• King George Tupou VI, formerly Crown Prince Tupouto'a Lavaka Ata.
• Promoted to the throne in 2012, following the death of his brother: King George Tupou V.
• Celebrations started on Saturday and will run until July 7.