Scarpia: What's new?: Stephen Johnson wonders whether the good old days were really as good as all that

AS ANYONE who has been through what used to be called the Iron Curtain will know, visiting Eastern Europe can be like going back in time. I remember strolling across the Charles Bridge in Prague in the summer of 1988 and finding it full of long-haired, kaftan-clad guitarists crooning 'Imagine' and 'We Shall Overcome'. One shouldn't mock - after all, they did overcome. It was an unsettling feeling all the same, and it returned with a jolt during Monday's Agon New Music Ensemble concert in the South Bank's Czech Festival.

On paper this looked like an interestingly balanced programme, three pieces from the Sixties or early Seventies in the first half, three Nineties products in the second, with something from just before the Velvet Revolution as a finale. In fact, without the booklet, it would have been almost impossible to guess what was when. OK, Zbynek Vostrak's free-floating Secret Fishing - conceived, we were told, 'as a result of Vostrak's individual mystic experiences' - did conjure memories of joss-sticks, sag-bags, Guevara posters and what Frank Zappa calls 'trendy chemical amusement-aids'. Otherwise it was a barely differentiated sequence of modernist grimaces and postures.

In fact the whole thing was like a horrendous revenant, the ghost of new music concerts long past. All the peripheral details were right: the audience barely outnumbering the players, the programme-notes more entertaining and communicative than the pieces. It was a salutary reminder. With so much of today's new music blandly minimal or eager to please, it is tempting to look back on the modernist Sixties and Seventies as a golden age of courageous exploration and revitalising shock, everybody busily polishing up their doors of perception. There were good things, of course - 'happenings' that really happened. But quite a lot of them were like this: frenetically self-indulgent but, for all the energy expended, eminently forgettable.

Will authenticists of the future attempt to recreate this sort of thing? The New Queen's Hall Orchestra has reached Rachmaninov, and last Friday they brought a Barbican audience period-instrument Elgar - the Enigma Variations with fruity narrow-bore trombones and a woodwind section that deliciously refused to blend (the same could be said, less happily, of the strings). It seems they could go much further: not so long ago Christopher Hogwood pointed out that the bassoon sound Stravinsky would have expected in the famous Rite of Spring solo would have been very different from what we hear today - apparently it's too easy now.

Interest in instruments and performing styles of the past is actually a much older phenomenon than many seem to think - how to perform Bach 'correctly' was an issue even in Mendelssohn's day. But we do seem to have come to the end of another phase in its history - the period in which the shock of the old replaced the shock of the new. Authenticity has become established. Period style performances took four prizes at last week's Gramophone Awards.

So where do we turn now for the new, the genuinely challenging? As the Agon concert suggested, there has probably always been a lot less of it around than fashionable voices have claimed, but the present aspect does seem particularly bleak. Perhaps we have finally arrived at the position foreseen some years ago by Pierre Boulez, where 'categories of the establishment and the avant-garde make no sense any more', where we live in a 'blotting-paper culture which absorbs everything'.