Cecilia Bartoli, Barbican, London <!-- none onestar twostar threestar fourstar -->

It's all very well enjoying the sound of Cecilia Bartoli on CD executing another astonishing vocal feat, but there is nothing quite like hearing her in concert. Records can hide tiny flaws, retakes make each minor detail perfect, but in a recital all is revealed. Bartoli has little to fear from such exposure, even if the voice shows the merest signs of fraying since her last British recital appearances. On a concert platform, with nostrils flaring, pony-tail tossing and arms twitching, she offers as much to see as to hear.

Bartoli, bringing forgotten or neglected composers from dusty library to international prominence, has based her current project on works composed during the early 18th century, when a papal decree prohibited certain music. There's a dangerous edge to the music in the way she sings it, and Pope Clement XI must be spinning in his grave.

Opera was out, with anything theatrical denounced as a bringer of sin and damnation. But thanks to some cunning priests - doubling as patrons and poets - composers were enabled to write in an operatic style.

Bartoli's coloratura mezzo voice may not be quite the same as the castrati of the time, but her silvery colour, alternately flamboyant style and captivating pianissimo make for riveting listening. Arias by Scarlatti and Caldara make tremendous demands in terms of breath control and vocal agility, but in Bartoli's interpretation they're much more than mere sprays of glittering fireworks.

Seldom has Handel's "Lascia la spina" sounded so meltingly beautiful. As well as some vigorous instrumental spots, vitally performed by the fresh-sounding Basel Chamber Orchestra, there were opportunities for oboe and trumpet to duet triumphantly in tongue-twisting, finger-twiddling dialogue with Bartoli. Julia Schröder on first violin proved a flexible partner to Bartoli's whimsical solo line, but it was the singer who directed the small band, using her whole body.

The throbbing "Si piangete pupille dolenti" was, perhaps, the most heart-stopping example of Bartoli's complete artistry, at least until the first of her encores, "Ombra mai fu". Three of the vocal numbers, including the magical "Io sperai trovar nel vero", are not on the Opera Proibita CD, which has topped the pop charts in some parts of Europe. Singers may come and go, but Bartoli is a truly amazing phenomenon.