It should be said at the outset that in her heyday Kiri Te Kanawa possessed one of the most remarkable voices in the world, a soprano of such allure and opulence that you simply surrendered to its beauty and overlooked the occasional flaws in her methodology. She was - and still is - primarily non-interventionist, allowing tone and line to carry the sense of the music rather than rooting the meaning of a song or aria in its words.

Like many singers for whom sound is all, however, her approach has not withstood the test of time. Te Kanawa is now in her late 50s, and her recital with pianist Julian Reynolds revealed a weakening in her powers. The tone, particularly under pressure, has hardened. The climax of Berlioz's Le Spectre de la Rose is marred by a pulse in her voice, when once it would have soared in ecstatic rapture. Duparc's La Vie Antérieure, plumbing the morbid, erotic depths of Baudelaire's poetry, needs a more voluptuous sound than she can now muster, while Poulenc's Les Chemins de l'Amour now lacks the requisite tang of cabaret toughness.

We do, however, hear intermittent flashes of what she once was. When she turns to Schubert's Gretchen am Spinnrade, there is an astonishing protracted diminuendo to silence at the words "sein Kuss", which tells us all we need to know about both Gretchen's naivety and her erotic wonder.

The filigree thread of sound that Te Kanawa employs for Schubert's Nacht und Träume is spellbinding, particularly given the inordinately slow tempo she adopts, and she gives us a delicious version of Hôtel, Poulenc's cheeky meditation on the pleasures of tobacco. Such moments, however, get fewer with each successive recital. Audiences still adore her, but those of us who heard Te Kanawa in her glory days can only be saddened by her decline.