The second concert in the Wigmore Hall's Kurtag series was a far more cogent and digestible affair than the first, a month ago. The programme demonstrated what an almost symbiotic relationship Kurtag has created between his own exquisitely chiselled pieces and the music of Bach, each setting off the other to best advantage. The Keller Quartet, Kurtag's interpreters of choice, interleaved his string quartets and trios with movements from Bach's Art of Fugue, presenting each half of the concert as a single, seamless span.

Though the Keller also included the slithering 1989 Ligatura for string trio, and a selection of pieces and arrangements for quartet, trio and two violins from one of Kurtag's typical collections-in-progress Signs, Games and Messages, the concert's centre pieces were his two most substantial mature quartets. Before the interval, the set of 12 Microludes, completed in 1978, was flanked by sequences of Bach. In the second half, a more elaborate enfolding of the two composers was built around the Officium Breve In Memoriam Andreae Szervansky from 1989, 15 even more fiercely compressed miniatures - a sequence of shuddering chords, skein of ghostly rising scales, a microscopic canon, or anguished melody unfolded over strumming accompaniment - which cohere miraculously into a single music statement whose tone is unmistakably elegiac.

The Keller play this music as if every note has its own priceless significance, and the way in which they juxtaposed Kurtag and Bach was perfectly calculated, too. Whenever the mood of Kurtag's piece became too suffocatingly introspective, a piece from The Art of Fugue would bring fresh air and a new perspective, each contrapunctus or canon played with just the right combination of chaste purity (the vibrato tightly rationed) and rhythmic life. A beautifully conceived experience and immaculately realised.