Kirkby/Florilegium, Wigmore Hall, London

Dame Emma Kirkby has come a long way since her vocal beginnings as a student at Oxford in the Sixties. It was she who led the way for vibrato-free singing to match vibrato-free Baroque instrumentalism in the first flush of excitement over "early music". Forty years on she's scarcely changed her voice still has that evergreen choirboy purity. Teaming up with the Florilegium ensemble as she often has at the Wigmore, they surrounded Bach's best-known cantata with rediscoveries.

We may now be familiar with the work of Bach's prolific contemporary Georg Philipp Telemann, but his Suite in A Minor with which Florilegium opened was a fascinating novelty; its final movement, based on Polish folk music, boasted rhythms and harmonies as wayward as any in Chopin. Brilliantly led by Ashley Solomon on recorder, the little band produced a muscular sound.

Then Kirkby joined them for a rarity by Frederick the Great's favourite composer Johann Adolph Hasse, in the form of a cantata whose floridness suggested the castrati for whom it had clearly been written. The imagery palpitated with lust, in its evocation of the seasons: the harmonic progressions were intricate, the melodic lines sinuously chromatic.

Kirkby loosened her vocal stays and invested her sound with more colour than I've hitherto heard from her, but one felt the lack of a David Daniels-type countertenor with a dramatic armoury to match the subject-matter.

Then came more instrumental novelties, this time from Johann Heinrich Schmelzer. If the first was constricted in its tonal frame, the second joyfully burst its bonds with more tunes purloined from Polish folk-music: interesting to find these proto-Bartoks digging out stuff from villages three centuries before the world-music boom.

And then came Bach's Ich habe genug, which raised more questions than it answered. So many great singers have performed this cantata that we all carry ideal renditions in our heads: Kirkby's light tone in this high soprano version worked charmingly, but left me unmoved.

The 17th-century English song she sang as an encore was, in contrast, perfectly suited to her voice and manner: horses for courses.