As viola player Sam Quintal’s introductory note celebrates, this disc ‘marks the culmination’ of the Jasper Quartet’s 10-year involvement with Aaron Jay Kernis’s string quartets. Having played and recorded the first two, they commissioned a Third from him in 2015, a work that ‘surpassed its two preceding quartets in complexity and difficulty’ and of which they made this recording in December 2017. Having the composer’s idiom so firmly under their fingers now, I do wonder about that ‘culmination’; I can quite imagine Kernis (b1960) might have a few more quartets in him for so committed and virtuoso an ensemble.

The Third Quartet, subtitled River, is cast in a Bartókian five-movement design, three substantial spans – ‘Source’, ‘Mirrored Surface – Flux – Reflections’ and ‘Mouth/Estuary’ separated by two shorter interludes, ‘Flow/Surge’ and ‘Cavatina’ (this last a hangover from the composer’s original intended model of Beethoven’s Op 131). Ebb and flow, ‘change and flux’ are the key elements throughout, with some vividly imagined and intense writing in the outer movements and moments of real delicacy between. The powerful image of the river that runs through the whole work (from source to estuary, indeed) derives from Romain Rolland’s Jean-Christophe, though Karl Ove Knausgaard’s autobiography proved even ‘more vitally influential’ for the work’s musical processes. The Jasper Quartet’s account is compelling.

The quartet’s previous discs paired Kernis’s First Quartet, Musica celestis, with Schubert’s Death and the Maiden (9/12^US) and the Second, Musica instrumentalis, with Beethoven’s Third ‘Razumovsky’ a year later (2/12^US). For No 3, they move away from the Classical era for the coupling, Debussy’s enchanting early Quartet of 1893. It makes for nice contrast and the Jasper’s performances of both are flawless in ensemble and intonation, expressively assured and beautifully balanced. The sound quality is first-rate.