Classical: All square after extra time

MORTON FELDMAN PLANET TREE MUSIC FESTIVAL CONWAY HALL LONDON

MORTON FELDMAN'S For Philip Guston - which received its British premiere on Friday - poses challenges very much in tune with the preoccupations of the Planet Tree Music Festival, and of its director Lawrence Ball. Advertised as four hours long, this composition for three performers - here, Dorothy Stone playing three kinds of flute, Simon Allen playing four tuned percussion instruments, and John Tilbury on piano and celeste - is named after the composer's painter friend.

Among the longest of the long works Feldman wrote during his last years - it was composed in 1984 - For Philip Guston taxes its listeners as well as its executants with soft, slow and potentially endless permutations of a limited vocabulary of single notes, motifs and chords. These are subjected to contrapuntal elaboration, modification and recapitulation, the note-to-note details of which are often rhythmically complex. One of the fascinations of listening to the composition is the impossibility of acquiring any detailed and comprehensive grasp of previously heard versions of these materials and their placings: a direct result of (and, if you readily submit yourself to the challenge, itself some justification for) the extended canvas Feldman deploys.

But while this can lead the sympathetic listener to search for fresh ways of listening, taking us into new areas of musical, and spiritual, experience, the complete abandonment of more conventional perceptions about how such music moves through time is rendered difficult by factors more interesting than the sudden realisation that you have developed a very sore behind. (Cushions and bean bags were much in evidence.) Knowing a little about how its composer put such pieces together, I find it impossible not to consider them as evolving shapes, with contours not so dissimilar from those of more dramatic and narrative musical structures.

Events around the two-and-a-half-hour mark, for instance: little solo passages (it's amazing how little solo or even duo work this piece contains), more silences, the prominent return of a four-note flute motif from the very opening, suggest the combination of new departures and gathering up of previous ideas that characterise a piece entering its final stages. For me, indeed, things could have happily concluded shortly after this. When what felt like a piano coda towards the promised four-hour point was followed by a further 35 minutes of music - concluding after four hours and 27 minutes - it all seemed simply too much.

The Conway auditorium is too frequently disrupted by people elsewhere in the building to be the ideal venue for such an enterprise. While the sounds were scarcely as soft and "sourceless" as they ideally should be - the American flautist, a Feldman specialist brought in for the occasion, was too loud, and too dominant, as well as occasionally a little out of tune - these performers demonstrated unusual intelligence and bravery as well as sheer stamina. A high proportion of a committed audience stayed with this special event to its sweet, rather inappropriately Arvo-Part- like, end.

Keith Potter