It is difficult to separate Ivan Zagni from his history. In his native England he was the rock guitarist who went "straight from Aynsley Dunbar to the church", finding a spiritual and intellectual recharge in cool Palestrina polyphony.

In New Zealand, 20 years ago, he helmed Avantgarage, the hippest ensemble imaginable. The classical set knew cellist Amanda Hollins and bassoonist Mark McEwan, rock'n'rollers had grooved to drummer Ben Staples and guitarist Mark Bell, and cellist Pam Gray was a prominent Pramazon and well-known in politico-performance art circles.

Zagni organised them into one organic band.

In 1990, he was the Auckland Philharmonia's first resident composer, and his Breath of Hope took us on a voyage down the Waikato, alternating hymnic serenity and coruscating brilliance.

This man, who can pick up a guitar and draw enchanted riffs from its strings, has a special affection for the orchestra.

On Sunday, Auckland Chamber Orchestra will present the first Auckland performance of Zagni's The Koeakoea.

It will be the first time the score will be performed intact, as the 1987 Wellington premiere did it on the cheap by eliminating violins.

It is a clarinet concerto in all but name, and Peter Scholes will be the soloist once again.

"Peter told me it was like having to battle," the pragmatic Zagni muses, "so I told him the koeakoea has always had to battle with the forces of nature to get from A to B, and this is reflected in the music."

And so the work reveals the song and the migration of New Zealand's long-tailed cuckoo, complete with lighting suggestions and narrative descriptions that led Jack Body in 1987 to suggest it could be presented with a speaker.

In fact, this evocative piece has no need for words.

Zagni points to a section in which a group of singers has to break small twigs, while solo violin and clarinet circle around one another.

"The clarinet is the koeakoea trying to use the nest of the white-eye, played by the violin. The twigs represent the sound of the bush."

This man is an ardent environmentalist - when I mention Breath of Hope he vehemently says, "This piece was all about the junk that has been dumped in the Waikato River" - and he also feels musicians are not being as adventurous as they might be.

"We have lost that sense of experimentation in music," Zagni says. "Back in the 50s and 60s there were some wonderful sounds coming out of the orchestra. They were pushing the boundaries, and it's nice when you're able to have a choir who are happy to snap sticks."

The human element is important to Zagni - one of the advantages of orchestras is that "you do have people behind every instrument" - and you sense a certain suspicion of the technological takeover of the past few years.

"You put your music on a computer and it's almost dictating which way you're going to go," he laments.

"It loses all its purity. It's so easy to copy and paste, and, in the end, I had to back off."

When, as Chamber Music New Zealand's resident composer, he was judging young composers' scores, the handwritten ones were always more welcoming.

"I love seeing handwritten music and, after a few listens, you feel you know the person behind the music better."

He is working again in the orchestral medium and has just finished a cello concerto. He tells of the torments and rewards of being a composer.

"You can be in your studio for months and, although you know you're going somewhere with your piece of music, nothing comes through. Then you write one little phrase and its heart starts to beat."

Performance

* What: Auckland Chamber Orchestra
* Where and when: Auckland Town Hall Concert Chamber, Sunday, 6pm