There’s a strain of disarming whimsy running through the English folk tradition that can make it seem quaint and disengaged from modern life. Opening for The Unthanks tonight in the National Concert Hall, The Bookshop Band occasionally shows a little too much of it. There are ukeleles, lots of upbeat tunes, and in ‘Smog Over London’ a singalong chorus with what must be the most stereotypically English line ever worked into a song: “Smog over London looks jolly splendid I’ve heard”. 

The duo’s USP is that their songs are inspired by books they’ve read. As a device for connecting with a literate audience, it has the advantage of building ready-made context for listeners, and it allows the band to be hugely prolific, often releasing multiple albums in a single year.

Where the books involved are genre pieces like the steampunk novel ‘The Strange Affair Of Spring-Heeled Jack’ or Ned Beauman’s ‘Glow’ thriller, the music created from them feels merely proficient, sweet and a little escapist. However, the band is capable of more substantial stuff, and a song based on Margaret Atwood’s ‘The Testaments’ is articulate, tough, and affecting, with Beth Porter’s mournful cello lines drawing out the pathos of the words.

After the interval, when Becky and Rachel Unthank step on stage with pianist Adrian McNally, it feels at first like more of that same whimsy. They chat amiably in their broad Geordie accents, there’s a mention of clog dancing, some easy laughs, and seemingly nothing more to trouble the respectable tranquility of the NCH on a Sunday evening. 

The Unthanks are appearing tonight to showcase a series of settings of Emily Brontë poems, composed at the Brontë parsonage on the recently-restored piano played by Emily during her lifetime. But there’s nothing of the tea-and-scones whiff of English Heritage about them: they’re resolutely modern, in places recalling Philip Glass or Max Richter, and their repetitive minor-key melodies work well with Brontë’s opaque but insistently rhythmic verse.

‘Lines’ is the apotheosis of that marriage of older verse and more modern music. It’s 7 minutes of allusive lyrics over a melody that circles around itself like a recurring dream, the sisters singing at times in unison, at times echoing each other in call-and-response, and at times breaking apart into close, keening harmonies. It’s genuinely moving.

Those close harmonies have been a feature of the Unthanks since their earliest days, and though they’re undeniably pretty, they’ve never distracted from the unflinching candour of the group’s songs. After the Brontë cycle, they sing pieces from across their back catalogue: recent songs from first world war writers, from their settings of words by Nick Drake’s mother, Molly, and from other recordings of the last decade.

The narratives in those earlier tunes often revolve around the straitened lives of the English poor, featuring fishermen who drown at sea, or heartbreakingly in ‘The Testimony Of Patience Kershaw’, a teenage mineworker, degraded and derided by the men she toils with but all too aware she has no other routes open to her. As another outsider voice whose humanity needs reasserting, Brontë is a perfect fit.

The final song after nearly 2 hours of music is ‘Here’s The Tender Coming’. Like many folk tunes, it has an easy major-key melody, and again it’s dressed in those gorgeous sibling harmonies. But it’s at heart a mournful tune, a lament sung by men forcibly pressed into service in the navy, and here it’s lent added poignancy by the rising and falling waves of McNally’s circular chords on piano. In these days of Brexit, it’s remarkable to hear music that focuses on place and people without giving in to empty nationalism, music that’s honest about the darkness of the industrial and colonial past while still remaining alive to the compelling beauties of the tradition.