"Global warming can be seen in the growth of the conch shell in terms of its layers," she explains. "If you cut across a conch shell you'd see the layers of the ages. It's profound stuff. Nature's profundity is often the spur to an artistic statement. This is where those of us lucky enough to be in that world pay homage in an abstract way, doing our little bit and reflecting that profundity back."
When the Herald spoke with de Castro-Robinson two years ago she had just written Tipping Point, another work sparked by the composer's concern for the planet's future. Does Clarion arise from the same pessimism?
"It's even stronger," she says. "As a parent you're hyper-aware of this kind of posterity, the passing on to generations. It's hard to see beyond things that are happening at the moment, with large parts of the world under water or on fire."
De Castro-Robinson has always been comfortable that once composed, her music must fend for itself, taking on whatever meanings the listener applies to it. Does she feel that way about Clarion and, before it, Tipping Point, which carry such strong messages of activism?
"I'm deeply appreciative of the power of music and the arts but after a while I don't want to be hammered over the head and told how to listen. The great composers – Beethoven, Mozart, Bach – don't shout at you."
For de Castro-Robinson, less is often more.
"If you want people to listen, write very soft music. If you want a class to shut up, leave a silence, speak softly, then you've got them in the palm of your hands."
De Castro-Robinson no longer needs to worry about capturing a class's attention. After an association of more than 30 years, comprising three degrees and 25 hugely influential years of teaching, she recently announced she's taking early retirement from the University of Auckland.
De Castro-Robinson says she's considered stepping away for a few years. She has been more vocal than most about what she sees as the school of music's shortcomings, particularly its controversial move away from the traditional conservatory model where the aim is to produce performing musicians. The change resulted in the loss of several staff, including long-standing friends and colleagues.
She sounds demob-happy with what the future holds – she mentions creative writing, learning to play saxophone, and various residencies – but she admits leaving the university was a wrench.
"I'll miss it a huge amount. I've loved my time there; it's been wonderfully collegial and stimulating. My colleagues and students have been endlessly interesting, frustrating, deeply enjoyable, and I'm still very much part of the music scene, but I'm on to new things – most of which I don't know myself yet."
Lowdown
What: Clarion: Music by Eve de Castro-Robinson, for Auckland Arts Festival
Where and When: Spiegeltent, Aotea Square, Monday, March 16