Ex Cathedra, St Paul's Church Birmingham

Is it possible for a carol concert to have a cult following? Ex Cathedra's annual Christmas Music by Candlelight performances in St Paul’s Church have quietly grown into a Birmingham institution. The audience has evolved its own rituals: camping out through the long interval in the box pews, and sharing improvised picnics of mulled wine and mince pies.

The formula, devised by Ex Cathedra’s director Jeffrey Skidmore back when Birmingham's Jewellery Quarter was still lit by gaslight, is simple enough to allow creative elaboration: a candlelit sequence of mostly a capella, mostly modern choral music punctuated by short readings. These concerts have become a cherished refuge for music lovers uninterested in the sleighbells and schmaltz on offer at Birmingham’s major venues.

The secret is the deep seriousness with which every detail is realised, from the perfectly-gauged diminuendo as the choir processed down the nave to Alec Roth’s new setting of Petzold’s "Morgenstern", to Alex Mason’s thunderous organ improvisation, starting from the last chords of Bach’s "How Shall I Fitly Meet Thee" and sweeping in a single gesture, as the lights went up, into the final (and solitary) audience carol, "See Amid the Winter’s Snow". The whole programme was anchored by Bach chorales: the unbroken opening sequence, as singers called antiphonal chant from the balconies of the darkened church, and filed onstage to "Wachet Auf" before resolving into the warm expressive calm of Sally Beamish’s "In the Stillness", was particularly effective and carried out with masterly timing.

The group's distinctively English sonority and reputation for precision don't preclude passion

What followed was anything but a traditional carol concert. Skidmore never compromises in his programming, and while a few candied chestnuts studded the programme – such as Kirkpatrick’s "Away in a Manger" sung with honeyed sweetness and loving attention to phrase-endings – much of the evening would have passed as a virtuoso survey of contemporary choral idioms, with at least eight items written in the 21st century.

It was in these that Ex Cathedra was able to show its range in earnest. The group’s distinctively English sonority – tightly focussed tenors and bright, bell-like sopranos – and reputation for precision don’t preclude passion: there was a bracing ferocity to their tone as they sent the jubilant “Glorys” of James MacMillan’s "And Lo, the Angel of the Lord" skyrocketing into the roof. Or sensuality too: they threw themselves at Naji Hakim’s "Noël c’est la Joie" with an almost tactile pleasure in its lush harmonic curves and bounding “Alleluia”s. John Gardner’s "Tomorrow Will Be My Dancing Day" was despatched with an unforced, graceful swing that kept it just the right side of Songs of Praise.

Understandably, though, in this context, it was the more reflective items that struck home most profoundly: "Snowflakes", a 2012-vintage anthem by Alec Roth given a wondrous strangeness by a few delicate touches from the organ, John Tavener’s "O Do Not Move" (beautifully refined shading of the inner voices) and a performance of Herbert Howells’s "A Spotless Rose" that found a Gallic perfume in its pastoral harmonies. In such company "Long Road" by current minimalist-of-the-month Ēriks Ešenvalds sustained its length less effectively, though it was sung with comparable conviction.

Still, the mood had been created and sustained so compellingly that a few dips didn’t really matter. In the candlelit blackness, it was impossible to read the printed programme, and therefore to be aware that the arrangement of "Es ist ein Ros entsprungen" which, hanging in the stillness of St Paul’s in a shimmering arc of wordless harmony, brought to mind an image of the Aurora Borealis, was indeed by a Scandinavian composer: Sweden’s Jan Sandström. This concert generated its own magic, sending you out into a raucous pre-Christmas city centre night with a renewed sense of mystery and wonder.