St James Baroque / Kirkby, St John's, Smith Square, London

Time was when you couldn't turn on Radio 3 without hearing Emma Kirkby, the quintessential voice of "early music". And Kirkby's voice seemed to have come out of nowhere, because a vibrato-free soprano was an affront to everything the conservatoires stood for. But Classic FM voted her Artist of the Year, and she sold records: The Pure Voice of Emma Kirkby reached number five in the classical charts, and The Sweet Sound of Emma Kirkby did almost as well. Decca's latest, The Very Best of Emma Kirkby, looks like cashing in further on her singular appeal.

Her voice doesn't work for everyone and its scope is limited. She can't evoke the passion of Monteverdi, and her sound isn't meaty enough for Bach, with whom she tends to skate over the notes. Her Mozart doesn't have the necessary colour. But on her home turf - with Purcell, Dowland, Arne, Handel, and Vivaldi - she's ideal.

For her New Year's Day concert at St John's Smith Square, she plumped for Vivaldi and Handel, with ideal support from the St James's Baroque ensemble. From the moment she came on in her cloud of Renaissance curls, everything seemed right for the occasion.

Familiar though her voice was, it was still a shock when she sang her opening aria in Vivaldi's motet O Qui Coeli - the sound seemed incorporeal, almost shrill, and pretty much as one imagines the sound of the castrati, whose music she has made her own.

But her artistry soon shone through: not beauty of tone, more a matter of beauty in the way she shaped the liquid phrases and ornamentation. And what initially seemed a small voice was soon filling this big space with ease. Like all good Baroque singers, she goes for instrumental clarity, and when she trilled with the oboes her voice sounded like an oboe. One sensed the pleasure she derives from singing: joyful, without any trace of vanity. Handel's Silete Venti, in which she effortlessly matched the 14-piece orchestra - was a delight.

Equal honours must go to the violinists Rodolfo Richter and Clare Salaman, for the way they handled Vivaldi's Concerto in A minor RV 522. This perennially popular work, which Bach transcribed for organ, demands immaculate delivery from its soloists, which it certainly got here.

Since the concert had a title - Something Old, Something New - we also got two Arvo Pärt favourites, Summa and the ubiquitous Fratres. Nicely done, but not in the same league as Handel and Vivaldi: sculptures, rather than dramas on the wing.