"I like a conductor who can almost anticipate what I'm thinking and react in a way that shows his understanding of what is going on in my interpretation."
Yet, in the final count, conductors don't always inspire the same revelatory experiences that he often gets from chamber music colleagues.
"These happen much more when I'm playing composers like Ravel or Franck with my friends," he says. "It's amazing to find that someone else understands a certain aspect of the piece in a way that I haven't yet discovered."
Talking orchestras, Altstaedt is fascinated by the way that "each is a different animal, with its own spirit, sound and unique ways of reacting. There's always a different vibe going on and it's not always the big names that I've enjoyed playing with," he says. "In Britain I've had some wonderful experiences with the various BBC orchestras."
Altstaedt has particularly fond memories of his first Elgar Concerto, in Manchester, even if he felt "a bit of a crasher" playing Elgar in his own country.
As for Europe, he singles out the "absolute devotion" of the Tonhalle-Orchester in Zurich.
"Orchestras so often put too much store on just exploding in volume but, in Zurich, the emphasis is on the quality of the sound."
Altstaedt is known for his adventurous repertoire, choosing composers who include Gyorgy Kurtag, Wolfgang Rihm, Thomas Ades and Nico Muhly, and says he is thrilled to be tackling Dutilleux's Tout un monde lointain next week.
This score is the soul of subtlety, he says, inspired by the poetry of Baudelaire, with that reverberant image of perfumes, sounds and colours all speaking with one another.
"You almost get the sensation of tasting the sound."
He feels the French composer's music engages with listeners on an almost intuitive level, unlike Beethoven, whom he describes as a missionary, "always aiming at getting us together in brotherhood, and reuniting humanity.
"Dutilleux creates a world of poetry and illusion. This is a world that may not be part of our daily lives, but it can exist in our minds."
This music, that owes so much to the traditions of Debussy and Messiaen, is also eminently approachable.
"Even those who are not into contemporary music will relate to its extraordinarily wide appeal.
"I've not heard anyone say anything but, 'Wow. I've never heard anything like this before; so wonderful, imaginative and colourful, so mysterious and beautiful'."
What: Auckland Philharmonia Orchestra
Where and when: Auckland Town Hall, Thursday at 8pm
