Two other worthy versions of Morton Feldman’s String Quartet No 1 (1979) – by The Group for Contemporary Music (originally on Koch, subsequently reissued by Naxos) and by members of the Ives Ensemble on Hat Hut – are around and about but this new one by the NYC-based FLUX Quartet leapfrogs into an easy pole position.

Feldman’s String Quartet No 1 marked an important point of transition. The motivic tics of his late chamber music – key works such as Patterns in a Chromatic Field, For John Cage and Piano and String Quartet – all derived something from the gestural DNA of this quartet, which was itself a distillation of Feldman’s earlier music. And the FLUX Quartet give us what amounts to a director’s cut: a wilful and unhurried performance that goes big on the small details.

The FLUX Quartet’s approach puts Feldman in the wider American tradition of open-ended form, pieces that travel with their material rather than resolve anything: the world of Charles Ives, Jack Kerouac and Gary Snyder. The Ives Ensemble present a neatly finished and concluded piece but the FLUX Quartet chisel and shape this compositional object into being in front of our ears.

Which doesn’t make it easy for us, or for them. The performance clocks in at 90 minutes – a whole 14 minutes longer than the Ives Ensemble – and their slow, deliberate tempo pursues Feldman’s structure to the very point of disintegration. Moments of harmonic arrival are big moments indeed. A sweet meets-sour descending chromatic flutter becomes a moving marker on the landscape, and there are others too; otherwise we’re eavesdropping on an uncomfortable struggle to put music together, a structure that keeps collapsing under the strain, leaving disorientated lines to find their anchor as figurations splinter: pizzicatos falling to the studio floor like a sculptor’s debris, sustained harmonics twisting into outlandishly counterintuitive shapes.

Mode present the piece over two CDs, while a bonus DVD (with 5.1 surround sound) lets you hear the 90-minute structure unbroken. The sound is exceptionally rounded and deep, and two early string quartet miniatures, Structures (1951) and Three Pieces (1954-56), complete this catnip for Feldmanistas.