Monochromatic Light (Afterlife) by Pulitzer-winning composer and multi-instrumentalist Tyshawn Sorey demands patience. Subtitled “A meditation on Morton Feldman’s Rothko Chapel”, the work uses a similar ensemble – percussion, keyboards, a viola, a choir, a solo voice – and a similarly abstract dialogue of rhythms and pitches to Feldman’s 1971 tribute to the US painter. But where Feldman’s meditative soundscape lasts half an hour, Monochromatic Light sprawls across 80 minutes and discloses only in its final bars a second vital anchoring in the African American spiritual Sometimes I Feel Like a Motherless Child.

Such a score is not ideally experienced from a hard pew in a hot church during a week of record-breaking temperatures. There were moments between its opening, barely detectible murmur of tubular bells and its closing revelation of the bass-baritone soloist’s single line of text (pieced together syllable by syllable over 50 minutes) when I struggled to hold on to a sense of musical architecture, when the pinpricks of dissonance and slow-motion scatterings of instrumental lines began to feel meandering. Other details offered more rapid gratification: elemental rumbling on bass drum and timpani using sticks with heads like candyfloss; a glistening sheen of bowed marimba on a rare, mill-pond calm octave unison from the choir; wild bass-baritone melismas plunging acrobatically across the voice.

For much of the work’s European premiere in St Giles’ Cripplegate, Sorey himself sat motionless on the podium. He raised his arms only to direct the choir’s entries, his movements leisurely curves as the BBC Singers produced wordless notes so pure – their blend so clean – they might almost have been synthesised. That luminous shimmer set off both the sometimes gritty, sometimes stentorian, always intensely characterful singing of bass-baritone Davóne Tines, and Ruth Gibson’s equally charismatic viola playing – the densely packed tone of certain bow strokes, the harsh catch of others and the harmonics she summoned as if with no bow at all. Positioned on either side of the performance space, George Barton (percussion) and Siwan Rhys (piano and celesta) of GBSR Duo were in constant communication, tireless in their subtle exploration of music that seems to cherish its own mysteries.