When musician Martin Green dreamed up a story involving an eccentric folk song collector, a free-spirited Scot modelled partly on Yoko Ono and a love story in which they leave messages for each other in a series of archive recordings, he intended the result to be a theatrical spectacular in which the audience would assemble in a tent to have their minds bent and their ears assailed. What’s not to like in that lot? Not much, though just in case Green also threw in some Morris dancing and a hefty dose of late 20th century rave culture.

London’s South Bank Centre was looking forward to hosting the show this summer and the Edinburgh International Festival had it inked in for its 2021 programme. Then Covid-19 happened. Undeterred, Green and his raft of collaborators – among them theatre director Wils Wilson, dramatic powerhouse David Greig, actor Alison Peebles, electronic musician James Holden and Adrian Utley, guitarist in Mercury Prize-winning trip-hop legends Portishead – have turned the show into something else entirely.

It’s called The Portal and it’s billed as “a fictional podcast for unusual times”. It’s narrated by a character known as MG (voiced by Green, one third of Scottish folk supergroup Lau) and it begins with his encountering a figure known as The Tup during a May Day Morris dancing routine with his father. MG is nine at the time of this first meeting. The year is 1988, the height of the rave era and a period often referred to as the second summer of love. Not for MG.

The Tup is actually a costumed Morris dancer done up to look like a massive ram. The young MG knows this but nonetheless the creature infiltrates his dreams and stays with him into adulthood, a demonic presence always at the edge of his subconscious. He can’t shake its grip on him but when he sees a photograph of the very same Tup in a book about folk dances, it sets him on the hunt for answers, which in turn leads him to the work of folk archivist and collector Etteridge (voiced by Dylan Read) and to Etteridge’s soul mate, Angela (played by Anna Russell Martin and Alison Peebles). She’s 90 when MG tracks her down but we hear her and Etteridge’s love story in flashback, and in the battery of recordings deployed throughout the podcast’s 12 episodes as it flits between eras.

“We had been talking about an audio version anyway because there was so much sound in the show and we had made such a quantity of sound design for it,” says Green from his house in the Midlothian village of Pathhead, also home to a bevy of Scotland’s folk and jazz talent and where he lives with his wife, Shetland-born musician Inge Thomson. “But right at the beginning of lockdown it became clear pretty quickly [we couldn’t do the live performance] and fortunately for us all the commissioners were happy to make that change. It was a surprisingly happy shift to audio and I’d do more of it.”

It also helped that otherwise busy collaborators such as Utley, Holden and sound designer Eloise Whitmore, who worked on acclaimed BBC podcast Tunnel 29, all had time on their hands (and in Utley’s case, a home studio in which to record music).

The genesis of The Portal’s plot lies in Green’s own family history. Born in Sheffield and raised in Cambridge, his father actually was a Morris dancer and as a boy Green was indeed taken to dance in the May Day dawn. Later, he became involved in the free festival circuit around Cambridge, which often had folk music at its root but which intersected with the New Age traveller communities that were such an important part of rave culture in the late 1980s and early 1990s.

“Being a kid I wasn’t really aware of rave but I always thought it was interesting that during that period we were all out there dancing in the dawn, in our own ways,” he says. “I feel like I saw something of the rave culture and I’ve always felt that it was more similar to traditional music in its social set up than I might have expected, in terms of people being aware of the legacy, of how the music had moved and who its pioneers had been at various points.”

In The Portal Green builds on both the differences and the similarities between rave culture and folk traditions. His two main characters, Etteridge and Angela, embody that fusion of freedom and constriction .

“One of our characters is a folk song collector and he is quite conservative and he just watches people and writes down what they do. Our other character jumps in and is ready to experience anything life throws at her and as a result is able to find herself in lots and lots of social situations just because people want to hang out with her. So those two ideas – that you can watch from afar or get stuck in – that was the beginning of the journey. And then there are bits and pieces of my own experiences of Morris dancing and clubbing and how at various different times you either feel like you’re watching the world or getting stuck in.”

Angela’s journey is the most fun and includes her making a series of experimental recordings in the 1960s using what today we’d call found sound. Here, Green has in mind Yoko Ono’s avant-garde albums made with John Lennon and also Revolution 9, a sound collage Ono co-created with Lennon and George Harrison and which features on The Beatles’s self-titled 1968 album, also known as the White Album. “Angela goes off and makes these wild and interesting recordings, at one point managing to get an LP of documentary recordings into the album charts and sparking a short-lived interest in a more popular form of documentary recording,” says Green.

Aspects of the lives and characters of Delia Derbyshire and Daphne Oram, stalwarts of the BBC’s fabled Radiophonic Workshop, also went into the creation of Green’s heroine.

Another idea that’s explored in The Portal is the nature of folk music collecting itself and the inevitable act of censorship, conscious or unconscious, which occurs in that process. Etteridge is based largely on Cecil Sharp, who gathered thousands of songs in England and Appalachia in the Edwardian era, and partly on American ethnomusicologist Alan Lomax and eccentric composer and folk music collector Percy Grainger.

“On the one hand it’s amazing that a load of stuff got collected because we might not know anything about it otherwise. On the other hand we get a very particular view of a scene because of the people who collected it and their own moral interests or their own sense of what is a nice national identity to present. Both those things are worth considering. It happens all the time in selfies as well – as we document, we’re all looking to present a very specific idea and we can’t escape that. There is no true documentation, I don’t think.”

All in all The Portal is quite a trip, and one it’s worth wearing headphones to enjoy. There’s also an album available featuring full length versions of the music in the podcast, and Green hasn’t given up on the idea of seeing The Portal staged one day.

Until then, he’s continuing with the day job: Lau have already released two live albums this year and undertaken a series of online ‘hangouts’ in which Green and fellow band-members Kris Drever and Aidan O’Rourke jam from their homes in Glasgow and Edinburgh respectively. Another one is planned for this evening – 8pm on the band’s Facebook page – and, First Minister permitting, there are hopes that a live gig can be arranged in front of a small audience in December.

“But we’re also doing something we’ve been talking about for 10 years which is making an album of traditional material,” says Green. “That’s been lovely, actually, just throwing folk songs that we love backwards and forwards.”

Who knows what he’ll find when he digs into the archive?

The Portal is available to download free of charge from most podcast platforms. An album, The Portal, is out now on Reveal Records. Lau will be performing online at 8pm tonight.