There are signs of the new and the old merging in Graz, the Styrian capital and Austria's second city, host of the festival Styriarte.

There are signs of the new and the old merging in Graz, the Styrian capital and Austria's second city, host of the festival Styriarte. Most striking is the Helmut-List-Halle, a converted steelworks whose fabulously simple, stylish, almost Bauhaus interior, was the brain child of the conductor Nikolaus Harnoncourt, 74, Graz's favourite son.

Wooden-clad, the hall sounds extraordinarily pliant and responsive. And it was this acoustic that enthralled in Harnoncourt's visionary reading of Telemann's The Day of Judgment, one of the most cracking oratorios between Bach and Haydn, with Vienna's phrasing-perfect Arnold Schoenberg Choir, four sizzling soloists and - best of all - Harnoncourt's Concentus Musicus Wien, the archetypal period-instrument group, now half a century old.

Telemann penned this irresistible masterpiece aged 81. Forget the occasional hackwork of his 46-year stint as Hamburg's Kantor. Rather, think Bach's B Minor Mass. Key to this awesome four-part work is the text by Pastor Christian Alers. Two riveting sections dish up a chamber-of-horrors of mocking atheism and lightning blasts (the Lisbon earthquake shook Europe's nerves just six years earlier); the crux comes at Jesus's noble calling to Judgment; the culmination is one glorious Believers' paean, led by St John the Evangelist: the music is 90 minutes of rapture. Why do we never do it?

A shivering introduction to Part I and skittering strings set the standards. The thrilling German baritone Thomas Mohr - clearly told to ham it up by Harnoncourt - launched the fireworks. In this classic piece of writing, Alers pits Mohr's naughtily attractive Disbelief (" Gericht? Ich lache die Gefahren" - "Judgment? Pull the other one") against Reason (the lovely mezzo Elisabeth von Magnus, by turns censorious and melting), Mockery (the Austrian tenor Herbert Lippert, a master of the snakily chromatic) and Religion (a searing entry by the Salzburg soprano Genia Kuhmeier). With a superb added Believers' chorus, Disbelief is consigned to the sociological rubbish heap.

All these storms send shivers down the spine, but it's when Telemann lets light break in - with Lippert's Archangel, just one disarming chorale and Mohr's ejection (now as Christ) of the Feinde Gottes and his serene greeting to the Blessed - that this astonishing work is lifted to a new plane.

A mere glimpse of Harnoncourt's expressive hands and famously beady eyes revealed how he electrifies his performers. Infectious. If only he'd bring it to London.

Festival runs till Sunday ( www.styriarte.com)