CONOR O’BRIEN has just brought out a critically acclaimed indie-folk collection of songs Darling Arithmetic which, intimate and delicately crafted as they are, might seem unsuitable for the vast space which is the Barbican Hall.

Not a bit of it. The five-piece band confidently take the plunge with the pensive album’s title song and instantly O’Brien’s sparse, minimalist sound is augmented by a sophisticated arrangement that adds a subtle, highly expressive power and weight to the music.

Measured double bass, percussion variously struck and caressed with mallets and brushes, a harp occasionally adding colour, a mellotron, a short trumpet and superb guitar work by O’Brien combine brilliantly.

The sound metamorphoses into a mesmerising, slow-paced crescendo that explodes into a wall of sound on the anthemic and spellbinding Little Bigot, with its command to “Throw that hatred on the fire,” the anti-homophobic Hot Scary Summer and the castigation of the inertia plaguing care for the environment on Waves: “No time for innocence or sitting on the fence.”

The songs boldly combine the heart-on-the-sleeve confessional with broader concerns about prejudice, the environment and need for courage “in harmony with something other than your ego.”

O’Brien’s voice holds the key — it has fascinating range and his extraordinary ability to modulate it with perfect precision to suit every line sung is glorious.

Classics like the melancholic Nothing Arrived are offered with pruned-down instrumentation to surprisingly good effect, attesting to O’Brien’s creative daring in testing new arrangements on old favourites.

The hit from the Awayland album My Lighthouse — dedicated to his sister — ebbs and flows, with its captivating melody underpinning the heart-rending lyrics of: “We’ll drink to the gentle and meek and the kind/And the funny little flaws in this earthly design.”

Alongside the masterly musicianship of the band, it is O’Brien’s sincerity that the audience is here to experience and at the end there’s a standing ovation akin to cathartic communion which testifies to that.

Catch this magnificent band if you can — you’ll leave with a spring in your step if you do.

Review by Michal Boncza