Auckland's orchestra has added its voice to calls for Radio New Zealand to scrap plans that will gut its Concert programme.

RNZ plans to shift Concert to the lower quality AM frequency, a move it said would free up space to build a new music channel based in Auckland and aimed at youth.

The content will also be downgraded. Its expert presenters will be shown the door and feature programmes scrapped in favour of an automated playlist broadcast around the clock.

But classical and jazz music lovers are fighting the move with more than 16,000 people having signed by Saturday afternoon a petition opposing the move by the publicly-funded broadcaster.

Opponents include opera legend Dame Kiri Te Kanawa, who has likened the proposal to gut RNZ Concert to scrapping the All Blacks, and former prime minister and arts minister Helen Clark, who tweeted it "equates to a dumbing down of cultural life in NZ".

"There is a pattern here of destruction of cultural services available to New Zealanders," Clark said.

Dame Kiri said it would be "an inestimable blow to the arts in New Zealand".

Today, Auckland Philharmonia Orchestra chief Barbara Glaser urged the orchestra community to support the petition. She said classical and orchestral communities are "deeply shocked and horrified" about the "drastic" changes.

"We're extremely distressed about this dumbing-down of the arts in our society," Glaser said.

RNZ Concert is home not just for orchestral music, but for New Zealand artists, she said.

"This would be a devastating loss to our arts and culture sector."

In a tweet Thursday, Clark referenced Minister for Broadcasting, Communications and Digital Media Kris Faafoi and Finance Minister Grant Robertson, and said "Hope ministers will take an interest in this very concerning @radionz decision".

She said the decision appeared to have been taken without public consultation and asked, "who's in charge?"

A tweet by Robertson in reply said he was advised it was still a "consultation" and "we will be talking to RNZ about their options".

Meanwhile, Glaser said the assumption classical music is elitist was not true today.

"Our diverse audiences and engagement with young people through our education and outreach programmes is testament to that. We know the same is also true of other orchestras and music organisations across the country."

The APO is calling on fans to sign the petition to keep the Concert programme on FM and retain the presenters.

The petition says Concert FM is the only station in the country playing jazz and classical music with world-class presenters, but there are dozens of stations providing the content the RNZ board wants to replace it with.

The move was against RNZ's charter to "reflect ... artistic diversity", and provide programmes which balance special interest with those of wide appeal.

But an audience of 170,000 appears to not be enough for RNZ's decisionmakers who want to use FM to reach a bigger audience.

RNZ Concert's FM stereo frequency is to be taken over by a new music station targeting younger, more diverse audiences.

RNZ chief executive Paul Thompson told Mediawatch the decision was part of the public broadcaster looking to attract a younger audience.

"We are thinking five and 10 years ahead. We need to start to connect with younger New Zealanders," Thompson said.

"We are expanding our services off our current resources. There are some tough choices in that but this is a really good story of RNZ getting to more New Zealanders."

The news came days before Broadcasting Minister Kris Faafoi announced Cabinet had approved a business case to examine the viability of merging TVNZ and RNZ under a mixed funding model.

He assured media that already commercial free platforms will remain that way. Faafoi said it's vital our media showcases a unique identity because foreign media can't grasp our culture and languages.

He said it's an opportunity to design a future-focused organisation, to better meet audience expectations.