For John Cage (1982) is one of Morton Feldman’s soft and patient late works. Inspired by Persian hand-woven rugs, it is a study in large-scale gossamer structure, and of a seeming mechanical symmetry and regularity that on closer inspection turns out to be rich in the variation of the handmade. Darragh Morgan and John Tilbury are ideal interpreters: they are both veterans of contemporary classical chamber music, and in particular of Feldman: with the Smith Quartet, they have recorded Feldman’s complete works for piano and strings (Matchless Recordings, three volumes, 2007–2016), and they have been performing For John Cage since at least 2006.

Supporting this work’s slow and soft surface is a profoundly demanding composition. Its challenge lies first in the violin’s technical difficulties: for instance, delicate artificial harmonics that can come rapidly upon one another. But the greater challenge is in its subtlety: For John Cage is over eighty minutes long on Morgan and Tilbury’s performance, and gives its performers extremely limited means by which to keep the music engaging for that time; there is very little breadth in note values or dynamics. Complete control of sound is therefore needed: when the texture is so thin, every sound becomes momentous, and a note played a touch too loud could ruinously slacken the tension. But at the same time, Feldman’s exacting requirements must not lead the piece to sound too ‘studied’. It is Morgan and Tilbury’s astonishing feat that not once do they lose concentration, and not once does the music sound anything other than organic and spontaneous. Here is where their years with the work has reaped dividends, and this listener was rapt.

Morgan, in the sleeve notes, talks about how he achieves this. First, he refrains from vibrato entirely; also, he uses a Baroque bow. Together, these decisions bring out the piece’s stillness and purity, even ethereality. The overall effect is of something glassen and sculptural, but there is also an unusual warmth in this recording: the warmth of the wood of the violin and the horse-hair of the bow, but also the warmth of intimacy; though it is due only to having to listen so closely to this whispering music, you feel almost as if you’re inside the instruments.

Even when stratospheric pianissimo harmonics sound unstable, Feldman’s vision comes through. One is reminded of how the imperfections in a handmade rug can add to its charm, and whether Feldman even wrote those impossible notes with this in mind.

As a final note, credit is due to the design of the accompanying digital booklet. In particular, the artwork on the front is a ‘plot’ by Leafcutter John (who is also a fine electronic musician in his own right). Feldman was profoundly interested in visual art (thus his Rothko Chapel and his many graphic scores, including, in a way, For John Cage), so it is a nice idea to have a musician-cum-artist involved in the album art. But more than that, the way the line (ink on paper, controlled by a robotic arm of Leafcutter John’s device) gently, confidently weaves its arcs, with subtle and controlled variation – and the way that, on closer inspection, you can see the uncontrolled unevenness of the line’s texture and thickness that reminds you of its analogue nature – makes it an inspired complement to Feldman’s music.

Morton Feldman – For John Cage by Darragh Morgan and John Tilbury is available to purchase from Diatribe Records. Visit https://shop.diatribe.ie/