image captionThe tape cassette features a recording of a previously unreleased song played by John Lennon in Denmark

A rare cassette recording of John Lennon and Yoko Ono will be auctioned in the Danish capital Copenhagen on Tuesday.

The 33-minute audio track was made by four Danish teenagers more than 50 years ago, and just months before The Beatles announced their break up.

It features an interview with the couple and what is believed to be a never-released song.

The auction house selling it estimates it could fetch between $32,000-50,000 (£23,000-£36,000) and is likely to go to a museum or collector.

'We were a bunch of hippies'

In January 1970 a group of schoolboys set out to meet the iconic musician and interview him for their school newspaper.

"We were a bunch of 16 year old hippies," says Karsten Hoejen, who made the recording. They were mostly interested in Lennon and Ono's peace campaigns, he says.

Locals had been surprised to discover the stars were staying in Thy, in the far northwest of Denmark.

image captionKarsten Hoejen was a teenager when he made the recording

The pair had come to spend time with Ono's young daughter Kyoko, who was living in the area with her father, ex-husband Anthony Cox and his wife Melinda.

Initially the stay went largely unnoticed. But once word got around, a news conference was held.

image source, Getty Imagesimage captionLennon and Ono held a news conference during their stay in northern Denmark

The four teenagers persuaded a teacher to let them attend and negotiated a ride to the venue, but they were delayed by a snowstorm and missed the event.

"It took a long time because of the snow and icy roads," recalls Mr Hoejen. "As we arrived everyone was leaving,"

However the boys and a few other late journalists were invited in anyway.

'Imitate what we do'

Armed with a borrowed cassette recorder and microphone, young Mr Hoejen taped the encounter, while his friend Jesper Jungersen took photographs.

"John asked me, 'where do you come from? A radio station?'. 'No, from a school magazine,' I said," recalls Mr Hoejen.

The meeting was "very cosy" and "relaxed". Lennon and Ono sat on a sofa, together with Kyoko, Anthony and Melinda Cox.

"[They] were sat with their feet on the table in their woollen socks." Mr Hoejen.

image source, Bruun Rasmussenimage captionLennon and Ono came to Denmark to spend time with Ono's young daughter

At that time war was still raging in Vietnam. Just months earlier Lennon and Ono had staged high profile peace-protests from their bed.

On the tape Lennon is asked, "but how do you think that people like me can help you with making peace around the world?"

"Imitate what we do," he responds. "Think what can I do locally?"

'The only place where this song exists'

At one point the couple joined in a Danish tradition and danced around a Christmas tree.

Then the former Beatle played guitar and sang the hit Give Peace A Chance.

image source, Bruun Rasmussenimage captionThe tape is thought to be the only recording of the song

The duo also performed a short tune called Radio Peace. It was written as a theme song for a radio station, Mr Hoejen tells the BBC.

"The radio station was never opened and the song was never released," he adds. "To our knowledge the only place where this song exists is on our tape."

'A recording like this is rare'

The recording was made just months before The Beatles announced their break up.

Decades later Mr Hoejen realised he was sitting on a valuable item and put the tape in a bank vault.

Now the old-fashioned cassette is on sale at Denmark's main auction house, Bruun Rasmussen in Copenhagen, together with an original copy of the school newspaper and 23 photographs.

image captionDanish auction house, Bruun Rasmussen, will is putting the tape up for auction

"A recording like this is indeed very rare," director Alexa Bruun Rasmussen tells the BBC. "We are not sure that there are any other recordings like this one, because it's an unofficial recording."

She says there are some other recordings from that time, however those are official press interviews.

The person who buys it will probably be "someone very passionate about John Lennon", she says.

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