Were some alien species to alight on a London concert hall - a hyper-intelligent hippopotamus, for example, or a human being under the age of 60 - they would be doubly confused.

First, by the unusual contract between audience and performer, which states that it is perfectly okay to whoop and holler at the end of a concerto, but never between its movements. This seems strange at first, especially if you're used to attending pop concerts where whoops and hollers are encouraged at all times. But the principle is sound: the silence is essential to the music, marking a change in mood and rhythm, and why should one huzzah ruin the quiet contemplation of everyone else?

The second point of confusion is a knottier problem. Instead of clapping in those short gaps between movements, the audience clears its collective throat. The first concert in Daniel Barenboim's ambitious Beethoven sonata-cycle at the Festival Hall last week was a case in point, 'case' having the appropriate medical ring to it. The January chill helped create a veritable cacoughany, as, between movements, the crowd released all the throaty vexations they had been nursing through the music.

One minute you were in rapt meditiation, admiring the Israeli-Palestinian maestro's instinctive rendering of the Hammerklavier; the next you were in a tuberculosis ward, gratefully fingering your BCG scar. What our hippopotamus would have made of this spluttering tribute I don't know.

The next morning, one reviewer commended the crowd for their concentration - not one cough during Barnboim's actual performance - but I wonder whether the odd wheeze here and there would have been preferable to the unnatural tirade.

Some concert halls have 'experimented' with cough sweets - but my colleague Norman Lebrecht warns of their attendant perils, recalling a Mahler's Ninth ruined by the scrunching of wrappers. He suggests spitoons of the things, unwrapped, at the end of each aisle, but this strikes me as a short term solution at best. Surely it would promote a free mingling of germs that would soon kill off the core audience? Bsides, the noise of sucking sweets - much like the sucking of false teeth that is a peril of watching opera at the Coliseum - is irritation itself.

Ordinarily, I see no good reason why concert and opera houses should feel obliged to bring in a younger crowd. Perhaps this is one?

But even I finally succumbed, tearfully clearing my throat in the final piece having held out so courageously. My fiancée bit the dust long before. Which left just one man unafflicted by the mania: Barenboim himself. Though judging by the gusto with which he mopped his brow, I think he feared the worst.

* Barenboim: Beethoven Sonata Cycle continues at the Festival Hall (0871 663 2500) until 17 February