In a disused fire station in Tollcross, Edinburgh, Shilpa Gupta stands, head cocked, beneath a row of speakers strung from the ceiling. There is a crackle, and a burst of noise reverberates through the space: a man’s voice, intoning the words “without revolution, there can be no proper peace”. As the voice dies away, a gentle susurration begins, like the distant clattering of bird’s wings. It resolves into a chorus of whispering voices. They seem to be coming from everywhere.

Suddenly, there is a loud mechanical squeal: across the room, a technician is attaching something to the wall with an electric screwdriver. Gupta wrinkles her nose. “Yes, that one is not planned.”

You don’t have to go far at this year’s Edinburgh art festival to encounter the sorrows of the modern world. In a former kirk just off the Royal Mile, the Scottish artists Ross Birrell and David Harding are exhibiting a film that repurposes Henryk Gorécki’s orchestral lament for the Holocaust, sung by refugees. Stroll into the National Gallery on the Mound and there, among the Titians and Tintorettos, you come face to face with a monumental Jenny Saville painting depicting the limp body of a Syrian child.

The voices press and jostle. We will not be silenced, they seem to say.

But in Gupta’s work those sorrows resonate both loudly and literally. Entitled For, In Your Tongue I Cannot Hide, the piece corrals the voices of 100 poets who have been imprisoned, and in many cases executed. The oldest hails from the eighth century; the youngest is the Burmese writer Maung Saungkha, who was arrested by the authorities in 2016 aged 22, for writing a poem in which he claimed to have a tattoo of Myanmar’s president on his penis (he didn’t, but served six months). Their words have been transformed into a piece of immersive sound art.

‘It has stretched my brain a little’ … Shilpa Gupta at work. Photograph: Ela Bialkowska

Even with the installation far from finished – “I think we’re about 12% complete,” Gupta says when we sit down in the canteen next door – it is an overwhelming experience, both piercing and claustrophobic. Many of the voices speak English, but alongside them are a babel of other tongues – Chinese, Russian, Arabic, Azeri, Hindi, Turkish, Urdu. Pinioned beneath each speaker is a print-out of their poem, skewered by a metal spike. Being among them, lights low, is a little like standing in a dungeon. The voices press and jostle. We will not be silenced, they seem to say.

Like much of Gupta’s art, this new project was born out of an earlier one; a 2011 work called Someone Else, which brought together books by authors who’d written under pseudonyms. Another was the darkening climate in her native India since the election of the right-wing populist Narendra Modi as prime minister in 2014 – an event that now looks like a grim foreshadowing of events elsewhere.

“Suddenly being a ‘liberal’ was an accusation,” says Gupta. She adds: “Social space is becoming dominated by certain voices who speak the loudest, claiming to speak for others.”

For, In Your Tongue I Cannot Hide turns that idea on its head, giving voice to poets who have been rendered abruptly voiceless. “My heart is now in my blouse / my blue blouse is now covered with blood,” reads one text by the poet Mohammad Reza Haj Rostam Begloo, who has been repeatedly incarcerated by the Iranian regime. “Give us back our Bahrain,” concludes another, even sparser, by Ayat al-Qurmezi.

One of the poets’ portraits exhibited at Yarat Contemporary Art Space, Baku, Azerbaijan, 2018. Photograph: Courtesy of the artist and Galleria Continua

“Poets, like artists, are dreamers,” says Gupta. “Even if they’re talking about nightmares.”

Gupta, who was born and still works in Mumbai, has an uncanny sense for the issues that dominate our age. One of her most famous works, 1:14.9 (2011–12), is a hand-wound ball of thread 75 miles long, a scale model of the 1,188.5-mile fenced border between India and Pakistan. Threat (2008–09) was a Carl Andre-like wall of soap bricks, each with that word emblazoned on it. An earlier sound work, 2008’s In Our Times, placed two speaker-microphones at either end of a pole. One emitted a speech by India’s first prime minister, Jawaharlal Nehru, made to mark partition in 1947; the other by his Pakistani equivalent, Muhammad Ali Jinnah.

Gupta likes her audiences to get involved: for Threat, visitors were encouraged to take a bar of soap home, tearing down the wall piece by piece. “There are many ways of creating, knowing and sharing,” she says. “We may not even realise it might be art.”

Assembling the new piece has been all-consuming. Not only did Gupta have to locate each text and source translations and volunteer performers, she then had to mix the installation so that it worked not on one or two speakers but 100. Her aim has been to make the composition as dynamic and intense as the language that makes it up.

“It is a bit like making music, or a feature film,” she laughs, showing me a dauntingly complex sound file on her laptop. “It has stretched my brain a little.”

The work has already been exhibited in Baku, Azerbaijan, where Gupta accompanied it with a stark series of line drawings of the writers, their faces and bodies symbolically erased. If she can scrape together the funds, she would like to distribute texts as pamphlets or an artist’s book. They have been a sort of gift to her; she would like them to be a gift to others.

Slightly to my surprise, she denies that there is overt politics on display here. “I dislike labels,” she says. “Political is a label.”

What drew her to make the work, then? She sits for a short while in silence. “It’s difficult to put into words. I just needed to.”