Cold Specks, Union Chapel, London

Al Spx (Rex Features )

When Al Spx sings away from the mic, her earthy vocal carries through the airy nave, proving this a fine match of venue and performer: a cavernous church, with its hard, cramped pews, and the stark spirituality of this Canadian singer/songwriter.

As Cold Specks, she has emerged from Etobicoke, Toronto, with a grave, sparse sound she has handily dubbed doom soul. Otherwise, her shadowy back story is one of dark hints about disapproving parents.

Having escaped to London, earlier this year she released debut album, I Predict A Graceful Expulsion, a set of soul-inflected folk ballads. While its title may suggest fire and brimstone testifying, the actuality comes with a puritan plainness. Now she has gathered a six-strong group to back her led by PJ Harvey’s drummer Rob Ellis, a sympathetic fit. They sensitively emphasise the minimal quality to her work, calling on influences that range from Minnesota’s Low to These Marble Giants.

Spx’s lyrics cover some heroically deep subject matter - death is never far away, pain close and redemption not so near. Usually, her voice comfortably carries such weight, as on the foreboding anthem "Holland", mirrored by her stark fingerpicking with its pure, metronomic quality.

Elsewhere, there is a hitherto hidden lustiness to the plaintive "Send Your Youth". She is more playful live than on record, applying her ability to recreate a sonorous chaingang to – of all things, and strangely effectively – the first verse of Will Smith’s theme to The Fresh Prince Of Bel Air, causing laughter and rhythmic clapping.

Also impressive is her reinvention of Swans’ "Reeling The Liars in" as a rollicking shanty which grows in force like a swelling sea. Occasionally, though, her delivery is so unadorned it comes across as merely matter of fact, notably on ‘The Mark’. She seems unsure how far to impose her vocal power on more meditative numbers and also betrays a lack of confidence by stumbling over anecdotes or looking to her band for reassurance. They ooze experience and carefully follow her resonant vocal on the relentless grooves of ‘Winter Solstice’ and "Steady".

Strange, then, that they sound clunky on quieter numbers, with the bass saxophone a parping distraction. This she loses for her finale, mounting the chapel’s ornate pulpit to deliver her powerful, acapella take on Woody Guthrie’s "Old Stepstone". Spx seems to have found her freedom in the UK, something you feel when see really lets loose.