But Mr Tilbrook wasn't entirely happy.

"You're clapping like Germans," he said at one point.

For a moment this caught me on the wrong foot. How exactly do Germans clap? Do they do it with very stiff hands? Do they do it with one hand over their head, ha ha? Do they pay Turkish immigrant workers to do it for them? Do they fall behind and then win with a couple of late claps, as against Mexico?

Then the penny dropped. He meant that the crowd were all clapping on the beat. Very stolidly. They were clapping on the first and third beats of the bar, as if they were accompanying a regiment marching by, and coming out with this lumpen, dead sound. It is a sound you sometimes get at the end of a concert when everyone in the hall is clapping loudly but randomly, and the separate claps suddenly coagulate into one enormous, repeated beat as everyone claps at the same time, as if some messianic dictator was about to appear.

There are other differences between jazz and non-jazz audiences. I have noticed, for instance, that when a rock fan hums or sings along to a favourite record, he is humming or singing a bit that is already there on the record. The jazz listener usually prefers to supply a bit that is not there - in other words, to improvise a missing solo, or bass line, or drum fill-in, and to embellish what he knows already.

In case you think I am leading towards the smug conclusion that jazz audiences are hip, and rock audiences aren't, let me say that when you have heard the real thing you don't make that kind of mistake. I heard the real thing last week, in Spain, in a swimming-pool near the mountain town of Callosa en Sarria. We English (a couple of families) were sitting at one end of the pool, and everywhere else there were Gypsies - attending a local festival, apparently, and taking a day off to swim. They swam rather Gypsy style, ie enthusiastically but mostly without bothering to change into bathing costumes. ("Maybe they're having a quick bath and a clothes wash at the same time," said someone.)

And when they weren't splashing, they were sitting at the tables with a drink and singing. One of them had a guitar. They could all sing. They sang flamenco, and they clapped, and my God, that was real clapping. I could follow some of what they were doing, the tricky across-the-beat phrasing, and I could hear the effect when they alternated the clapping so that it became very fast indeed, but generally speaking it was rhythmic clapping of a quality way ahead of any audience I have ever heard.

Of course, the funny thing is that in that case the performers were also the audience. These men and women were not performing to anyone except themselves - they were doing it for fun and didn't care who else heard it. This was a return to the blessed age when music-making was something that people did, not something that people listened to. David Owen Norris once said that music wasn't an object, as we all thought today, but an activity. Somebody else once said that real folk music was music provided by the talented members of the audience, and for once in my life I have seen it happening, and it was wonderful.

NB Any letters from readers pointing out that, by that yardstick, English football chanting is creative folk music, will be respectfully read and ignored.