Shakuhachi player Anne Norman was considering the "bureaucracy of lighthouses" when she learned of a potential performance space gouged into cliffs near Darwin Harbour.

She had performed in the Sydney Opera House and churches across Europe, yet she had never played in a 172-metre tunnel.

"I'm a musician and a musician is always looking for a good acoustic," Ms Norman said.

Anne Norman is the artistic director of Tunnel Number Five: Festival of Underground Music. ( 105.7 ABC Darwin: Emilia Terzon )

That was how she found herself hitchhiking westwards to Darwin last year for two performances in one of the city's World War II oil storage tunnels.

Built to store the Navy's oil after the bombing of Darwin, the tunnels were only briefly used during wartime before being abandoned and years later turned into a tourist attraction commemorating military history.

As far as venues go, they are damp, sultry and sweaty — but they also create unusual and mysterious sound.

"It's a perfect concert hall," Ms Norman said.

"I've played with a lot of reverb machines. This just beats absolutely everything. You are the recording engineer.

"If you turn laterally in the tunnel, it sounds like a bathroom. Meaningless. If you look down the length of the tunnel, you're setting up a standing wave pattern.

"They are absolutely exquisite. That's why I'm here and continue to keep coming back."

Underground music festival

This week Ms Norman came back to one of the network's longest spaces, "tunnel five", with a cast of singers and musicians for a week-long Festival of Underground Music.

Henk Rumbewas, his wife and young child led a conga line through the tunnel. ( 105.7 ABC Darwin: Emilia Terzon )

Included in the line-up was West Papuan-born Henk Rumbewas, a Darwin resident, singer and goanna-skin drum player that uses his birthplace's music to bring awareness to its ongoing struggle for independence from Indonesia.

"The first night I came into [the tunnel] I found it amazing," Mr Rumbewas said.

"This is like a loudspeaker. It's a very sensitive tool."

On Thursday night Mr Rumbewas and his young family sung throated calls to a long stretch of listeners seated in camping chairs with makeshift magazine face fans.

Drumming and joy merged when the audience was later called upon to join them in a conga line.

Yolngu songman Jason Gurruwiwi before his performance. ( 105.7 ABC Darwin: Emilia Terzon )

Also performing on Thursday night was Jason Gurruwiwi, a senior Yolngu songman from Galiwinku, and his nephew Guyundula Burarrwanga.

Joined at times by a lone yidaki (didgeridoo), the duo sang to each other from about 30 metres apart along the tunnel; their lyrics about turtles, cockatoos and baby dolphins entwining together as they walked closer to one another.

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"This takes my spirit along this tunnel to my people back there," Mr Gurruwiwi said.

The vast majority of the night's performers used wind instruments, including the yidaki and even plastic whirlies.

Sarah Hopkins plays the whirlies — plastic tube instruments that sound "like angels". ( 105.7 ABC Darwin: Emilia Terzon )

Ms Norman said these more subtle sounds were needed in a space that, in some ways, was itself a large wind instrument.

"When the yidaki player first came down, I saw the excitement in him. He played so subtly and so beautifully," she said.

"He played some of the traditional bungal and then he waited. He was just mesmerised and listening. He waited 15 seconds. Then he played again. A true musician.

"As a flutist, the control of an air tunnel is what you do. Here I'm controlling an air column that's 172-metres long.

"You have no idea how exciting that is."

Audience participation was invited during both the Yolngu and West Papuan musical performances. ( 105.7 ABC Darwin: Emilia Terzon )

Ms Norman said she wanted to keep performing in tunnel five, however one day hoped to top it with a different sort of above-ground venue.

"I've been trying for years to play in lighthouses. But the bureaucracy of lighthouses, you have no idea, with marine authorities, national parks, coastguards, often tourist operators," she said.

"I've wanted to do a gig in lighthouses where the audience sits on spiral stairs to the top and the performer is at the base.

"If you can get me that gig, I'll be all over you."