MUSIC / Review: All the romance of the circus: Robert Cowan on the lessons to be drawn from the opening concert of the South Bank's Deutsche Romantik festival

Thursday night's opening concert in the Deutsche Romantik festival began with a surprise appearance by the composer Hans Werner Henze. A somewhat professorial figure, he stepped up on stage, script in hand, to deliver an eloquent condensation of German Romanticism. Shy, earnest and a little tremulous, he gained in confidence the nearer he drew to images of 20th-century art.

His felicitous resume ran from the time of Napoleon through the Grimm Brothers' dictionary of etymology, the 'menacing forest whispers' of Weber's Der Freischutz, to Goethe, Holderlin, Spohr, Offenbach, Schumann, all manner of 'musical witchcraft' and on towards Expressionism, Surrealism, Art Nouveau and psychoanalysis.

Although initially bemused, the audience applauded warmly, then fell silent as Henze stepped down and Franz Welser-Most bounded in for that most startling of Romantic clarion calls, Beethoven's Fifth. A new CD single by the same artists had already given the game away: an impetuous, headstrong performance, occasionally breathless, but cumulatively powerful. At first, I feared that the 'Romantic' context might prompt a sequence of 'applied' Wagnerisms; but no, this was admirably bright and athletic, weighing in just a few decibels heavier than Gardiner or Bruggen and a good deal more resilient than either. And there were none of the textual optional extras we've come to expect nowadays, such as the Scherzo da capo or the long finale repeat: this was simply a rugged, straight-from-the- shoulder Beethoven Five, and a rather good one at that.

After Beethoven's tireless C-minor triumph, we heard Wagner's five 'Studies for Tristan und Isolde' to words by Mathilde Wesendonck. Again, Welser-Most kept things very much on the move, while Amanda Roocroft suggested serious longterm Wagnerian potential. The last three songs were particularly successful, although I would have preferred a less insistent vibrato and rather more tonal variety.

Wagner's sensual dreamscapes acted as a perfect bridge to Henze's dazzling Heliogabalus Imperator (after Antonin Artaud), composed in the early 1970s for Solti's Chicago Symphony Orchestra. 'The work has a circus- like quality to it, and listeners sometimes have the feeling that they are in the theatre,' writes Henze - an understatement, to say the least. Images of cultural revolution, reversed moral and sexual values and murder underpin Henze's exotic ground-plan, although the second part sets out actually to describe both El Algabal ('He who descended from the mountains') and those around him.

Musically, Heliogabalus Imperator is both sensual and provocative, a protean tour de force scored for a huge orchestra with a particularly wide- ranging line-up of percussion. It starts out like some wild, Messiaenic aviary, then slides among strings where purple harmonic patches help comfort the musically disoriented. There are Petrushka- like woodwind solos, a huge percussion cadenza a la Varese, bird-calls echoing above col legno strings - in fact a veritable witches' sabbath, and one that seemed to emanate from the same 'other side' that Henze had fleetingly referred to in his speech.

Certainly Henze has achieved a musical analogy for Artaud's verbal anarchy: I sat riveted, even while disgruntled audience members packed their bags and one lady in the choir seats leant incredulously towards the percussion. I got the distinct impression that this was not what most people understood as 'German Romanticism', a hunch confirmed when the concert finished and the hall emptied - rather quickly.