PROMS Xenakis, Elgar, Bruckner Albert Hall / R3

Long goodbyes, but few regrets. As swan-songs go, Elgar's Cello Concerto and Bruckner's Ninth Symphony are essentially hopeful pieces. There is sadness in Elgar's elegiac confessional, a feeling that that which is done cannot now be undone; there is anger, defiance, an overwhelming sense of catharsis in the grim reaping of Bruckner's last symphonic utterance - the one instance in his entire uvre where this God-fearing man actually shakes a fist at the Almighty and asks "why"? But in both cases there are answers - strangely reassuring answers.

Steven Isserlis's reading of the Elgar has been marinating nicely over the years. It's a very particular view, a private view. He doesn't reach out with the piece, he doesn't sell it in time-honoured fashion - but rather draws you into its confidence, to muse and to question. Bigness plays no part: the outgoing, "operatic" approach is not for him. You can always see behind the eyes of Isserlis's playing: listen, really listen, and he has a lot to say.

So concentration is all, and in Tuesday night's Prom it took him and us a while to settle. Tadaaki Otaka and the BBC National Orchestra of Wales were at once sensitive to his needs. You learn a lot about the conductor and orchestra in this piece from the way in which they "place" their response to the opening recitative. And then the violas have it - that autumnal tune. Isserlis didn't quite pick up here on the easy repose of it. Tension - the wrong kind of tension - was perceptible, if not wholly evident, and tension makes for tightness makes for unevenness. So some ragged co-ordination. But then came the scherzo, and suddenly Isserlis was Puck to Elgar's Oberon and you couldn't see bow or fingering for the speed of the articulation. The rest was fine, and personal, not least that moment in the dying breaths of the epilogue when the principal subject of the slow movement poignantly re-emerges. That's a special moment in every Isserlis performance of this piece. Beyond time and recall.

Time is, of course, an overriding factor in the Bruckner experience. From the moment those horns begin their summons from some deep and remote region, the Ninth Symphony, in keeping with every other Bruckner symphony, is an Odyssey that takes as long as it takes. There has to be that very real sense of evolution, of unfolding, of unharried ascent. Otaka kept his nerve, even though it meant testing his orchestra's. Bruckner is all about sustaining. And resisting the temptation to move on leaves an orchestra horribly exposed. The BBC National Orchestra of Wales did well to stay the course so concentratedly and with so relatively few sour or poorly placed notes. Otaka is a very centred, patient, conductor, and he instils as much in his players. The outer movements were possessed of genuine sense of awe at their enormity, the scherzo (the harmonic half-light of its opening bars chillingly tweaked at) proved an unsettling apposition of subversive war-like stomp and falsely ingratiating trio. As for that ending, Otaka seemed in no doubt as to its finality. A further movement would add nothing. It is finished. It is enough.

One wonders if Iannis Xenakis thinks so too. Earlier this year, in an Independent interview marking his 75th birthday, he said: "I'm getting very old now and older people don't care any more. They are waiting, maybe not for death, but for something different..." That Xenakis is unaccustomed to waiting was written all over his BBC commission Sea-Change, premiered at Wednesday's Prom by Andrew Davis and the BBC Symphony. The ferocious spirit that drove his notes and numbers into ever more furious and elemental contortions would seem to have deserted him. Sea-Change is a Xenakis torso with all the life-force taken out of it. The Tempest is its distant source of reference, so distant as to be barely recollected. Four trombones sound a deep pedal set "full fathom five". Bare unisons of woodwind, trumpets, and horns exchange sennets and tuckets. Glissandi feebly slither where once they would have seared. It's all over bar the shouting in well under 10 minutes. Except that there is no shouting. Not any more. Who'd have thought he'd go so quietly? Wednesday's Prom will be repeated on Radio 3, 2pm today