HK Gruber is making strangulated noises down the phone: "Aarghhhrraa! Floooargghaaraa!"

I fear for the Austrian composer/conductor/chansonnier slightly until he explains he is only repeating, wail for wail, a message left on his answering machine in 1998 by Hakan Hardenberger. It transpires Gruber is approximating the sound of a cow horn, an instrument/bit of animal he asked Hardenberger to learn for what was to be a new concerto.

Hardenberger, by Gruber's reckoning, was not a great cow horn player in 1998; in his defence, he was the world's leading trumpeter, which for most people would be enough. Not for Gruber.

"Hakan had never played a cow horn but he promised me he'd try," says Gruber. "I like to give musicians risky adventures."

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During time, Hardenberger came to grips with his new instrument and Gruber integrated it into Aerial, a (mostly) trumpet concerto that the New Zealand Symphony Orchestra performs in Wellington and Auckland this Thursday and Friday, with the composer conducting and Hardenberger on various wind things.

The work is now a favourite of Hardenberger, who has survived this risky adventure nearly 100 times. That's despite, Gruber claims, turning white when he saw the final score which requires him simultaneously to sing and to play, a technique known as multiphonics that was thought to be impossible on trumpet.

Remarkably, Aerial is the most conventional of the two Gruber works to be heard this week. Even crazier is Frankenstein!! (two exclamation points obligatory), a setting of children's rhymes that the composer describes as a "pan-demonium for baritone chansonnier and orchestra". What on earth is a pan-demonium?

"It's a party to which demons are coming." Ah, of course. "The demons are dancing, and someone unexpected arrives in the middle of the piece: Frankenstein!!" explains Gruber, relishing each of those essential punctuation marks.

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The text is by the Viennese writer HC Artmann, who also has a claim to fame as the German-language translator of nonsense poet Edward Lear and the Asterix books.

"Artmann was part of a generation that was against authority," says Gruber. "He wrote these children's rhymes but if you look behind the lines you will find hidden political statements."

You may have to look quite hard. Artmann refused to explain the subtext of his poems, reasoning that it's the audience's job to discover its own meaning. Gruber eludes attempts to be drawn on what the political messages mean to him, but the composer says the piece has a timeless and universal appeal.

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"There are archetypes, such as Mrs Dracula, who's flying and sipping blood. Kids can take it one way without making any associations but grown-ups can read the text and draw their own conclusions."

Frankenstein!! is by some distance Gruber's most popular work. That's partly the Stravinsky-meets-Kurt-Weill skill with which it is written and partly the bonkers joy of it. Unusually for the concert hall, it is a work where people are encouraged to laugh at the music. That doesn't include the musicians – there is an instruction written in the score that the players must remain poker faced throughout.

"Frankenstein!! is funny," says Gruber, "but if musicians react to the gags then it is cheap cabaret. Our goal is professional cabaret, which means that those who are making the gags never laugh."

They must be tempted. Early in the work the percussionist is instructed to blow up paper bags then throw them at the audience.

"Yes, but the percussionist has to do it in a rhythmical way," says Gruber, who is either being serious or simply remaining poker faced about his own joke. "The integration of these elements always has a musical function, it's not just an effect."

Not a joke, then. Because for all Gruber's madcap japes, he's a serious musician. In 2009 he was appointed composer of the BBC Philharmonic Orchestra, following in the steps of James Macmillan and Peter Maxwell Davies. He considers himself to have been a music professional since the age of 8 and at 10, he joined the Vienna Boys' Choir. In 1955 Gruber made his one and only previous trip to New Zealand as part of that renowned group, travelling here by ship and performing all over the country.

Lowdown
What: Frankenstein!!
Where and When: Michael Fowler Centre, Thursday, October 10; Auckland Town Hall, Friday, October 11.