Looking back in years to come, historians will find a musical time-capsule in the releases of the current period: recordings that commemorate, testify to, mourn, offer consolation or simply ponder this strangest of times. ‘The Covid 19 Sessions’ from American lower-voice ensemble Cantus is a classic of the new genre.

Recorded in March 2020, it’s the result of sessions snatched from the brink. With tours falling away and performances cancelled for the foreseeable, the octet got together in Minneapolis to shore some of their most treasured musical fragments against their imminent ruin.

Gathered from different seasonal and touring programmes, the result is inevitably diffuse, but some recurring ideas – sea voyages, the sky, songs of slavery – create an interesting constellation of thematic lines. The surging musical squall of Hugo Alfvén’s Gryning vid havet is all the more startling for being set against Japanese folk song Sunayama, lower voices rocking and soothing in a swelling sea-lullaby; Ešenvalds and Whitacre go head to head in their quest for sonic glow in Stars and Lux aurumque – though whether you prefer the brassy warmth of this TBarB ensemble or the cooler tones of SATB is a matter of personal preference.

A defining part of Cantus’s output is championing new music, and there’s plenty here. The quality, however, is variable. There’s a lot of fairly generic 21st-century Americana: blandly affirmative texts, homophonic settings, little counterpoint and no rhythm to speak of. More interesting is Abbie Betinis’s canonic Be like the bird, combining movement and stillness in its circling lines, and the gospel-folk simplicity of Ysaÿe M Barnwell’s Wanting Memories. Franz Biebl’s Ave Maria has become a bit of a modern classic – Rheinberger reinvented for the 20th century – and also gets a heartfelt performance.

Cantus are a class act vocally, prioritising personality and articulation over the kind of blend that dissolves individual voices. The result is forthright, folksy and direct, at its best in music of the same spirit. So listen to the Sibelius, the Biebl, even the Billy Joel, and maybe skip over some of the rest.