Kiri Te Kanawa, Royal Festival Hall, Londion

It was when she broke into "O mio babbino caro" that one felt those small tears welling. After all, it's not so very long since was our darling. Plucked from Covent Garden obscurity by Colin Davis, she swept hearts away with her Countess in Mozart's The Marriage of Figaro. The rest is legend: from her aristocratic Strauss heroines to Tosca and Desdemona, Kiri became simply Kiri - in a way, the Bryn Terfel of her era.

And here she was, hotfoot from her native New Zealand, whose Maori haka has been romping across our TV screens recently. Here was the great gal, a serene 60-plus, when she might be contemplating a twilight of master classes and endless juries, priming us with plums of the song repertoire, risking an unpredictable Royal Festival Hall acoustic to share with us the exquisite range of German lied and French chanson. Exquisite, it was; and, if one longed for a Wigmore Hall, her gift for turning Leslie Martin's gargantuan warehouse into an intimate experience was quite scintillating.

We heard that gift as she (belatedly) warmed to Mozart's "Abendempfindung", that poignant forerunner of Schubert from his Figaro period (with sentiments such as: "Weih mir eine Träne" - "Consecrate to me a tear"), through which whispers of the old Kiri peered; and the buoyant swirl of "Un moto di gioia", penned for Nancy Storace's successor.

She warmed to the French second half, in which the last stanza ("Car sur ton sein j'ai mon tombeau" - "For on your breast I have my tomb") of Berlioz's Théophile Gautier setting "Le spectre de la rose" was melting; in Duparc's "Chanson triste", the glassy brittleness of her fading voice was tinged with a lovely sensitivity.

Yes, fading it was. There were times when it rewarded more (an overpaced Schubert "Gretchen" apart) to hear the subtle cadencing by the pianist, Julian Reynolds - the fabulous lead-in to Schubert's "Nacht und Träume", or the rapt envois to Strauss's "Die Nacht" and Duparc's tolling, Mussorgskian "La vie antérieure". She can still conjure the old atmosphere, the Kiri purity: that crystalline aura still rules each note she utters. And at times she places it perfectly - witness the rising sixths of Mozart's Myslivecek adaptation "Ridente la calma", or Mendelssohn's "On Wings of Song". But countless notes in the German half seemed insecure, unsupported. A held semibreve might quaver rather than shimmer - or literally modulate before our ears, as if an attempt at enharmonics where there was none, so that passages in a single key seemed to span half a dozen. The more Kiri's alluring, closed-teeth smile mesmerised, the more those slightly metallic vowels pressed unabatingly forward. To live, German lied needs its back vowels.

Somehow, indeterminate vowels almost make chanson. Here, Dame Kiri seemed most at ease, drawing us in with a ballad-like whisper (Duparc) and bursting with life in Poulenc's perky "Hôtel" - brilliantly done - and "Les Chemins de l'amour" (shades of Trenet and Aznavour). Arguably, those, and her Spanish first encore, gave one that needed hot flush. What we had missed were her Gershwin, her Cole Porter and the operatic Kiri in joyous full bloom.