Paul Vallely: Warm broth is the key to comedy

Just what Aristotle thought of the spangly boob-tube is lost along with his theory of comedy. So I'll start with another venerable authority, my grandmother. The first time I ever went into a pub with her was one Christmas Day. We were on our way to a relative's house for the festive lunch and we had got off the bus early.

Perhaps she didn't want the embarrassment of knocking on the front door – not that anyone bothered to knock in those days – and entering before the appointed time to find the hostess in pre-prandial chaos. Or perhaps nipping into the pub was her way of seizing the opportunity to have her first adult-to-adult moment with her eldest grandson. Anyway, we found ourselves in the lounge bar just after noon, within half an hour of the opening time. The atmosphere was one of high-volume jollity, with many of the revellers evidently seriously inebriated after not much more than 30 minutes drinking.

"How come they're so drunk already?" I asked in adolescent wonder. "Warm broth soon boils," she replied, gnomically.

I thought about her adage in the middle of the Manchester Festival of Comedy this week. I was in the Comedy Store to see Tony Slattery guesting with a bunch of players in that kind of improvised sketch-making which had him never off our TV screens a few years back, before he had a nervous breakdown and retreated into a solipsistic sabbatical of staying home and staring at the bare floorboards. (He's much better now, thanks very much, I learn when I speak to him after the show.)

The trouble was I only arrived at half-time because of my yoga class (another story). Walking into a comedy show at the interval is a bit like arriving late at a dinner party, when everyone else is two or three bottles of wine ahead of you and being terribly amusing, or so they think. Not that Slattery and Co were unfunny; they were just as entertaining as those programmes you stay up late watching on the telly and think next day that you could have done with an early night really. But the rest of the audience was rib-tickled, which is what reminded me about the warm broth.

For it is not just your alcohol level but also your sense of humour that has to be warmed up.

I'll have to be careful here. Being theoretical about comedy can be a deadly business. Trying to find out yesterday exactly where Aristotle's theory of comedy got lost – it was said to have been part of the fabled second book of his Poetics that never survived – I went on to the internet and came across the following: "The theory of 'the comic' constructed in this thesis is called an 'ontic-epistemic' model: from a phenomenological perspective, human social perception, as opposed to mere physical perception. . ." Laugh? I thought I'd never start.

But it was too late, I was already on my way to formulating my own aesthetic of comedy – and based not just on the interaction of the Comedy Store Players and their boob-tube-wearing audience. ("People here get dressed up more than they do in London," one of the comics, Andy Smart, told me after the show as he surveyed a bar full of skimpily clad young women with naked flesh overflowing from lace-up corsets and other garments seemingly indifferent to the colder northern clime.) My theory was that before you can laugh you have to want to be amused.

The germ of this notion came earlier in the evening at another festival event, the start of Bruce Forsyth's national book-signing tour for his autobiography. It was in Waterstone's where the customers, I came to notice, fell into two distinct categories. There were the people who had come in to buy the new Ian McEwan and stared disdainfully at the light entertainment oik defiling their literary shrine. And then there were those who'd come especially in to see Brucie.

Some of these pretended they were looking at proper books but sneaked sidelong glances at the celebrity, an idiot smile playing, unknown to them, around their features. Others bounded up grinning, wanting to shake his hand, take his photo or ask him to write in their purchased copy "Nice to see you, to see you nice" or one of his other many catchphrases.

There was one key difference, it occurred to me, between the sniffy souls clutching their copies of Atonement and those who eagerly waited for the durable entertainer to say something funny (which by and large he didn't even attempt). It lay in their desire to be amused. Those who find a comic funny do so because they meet him halfway with their readiness to laugh.

Back at the Comedy Store one of the five-man comic team, Andy Smart, confirmed this. He and the others have been playing Manchester once a week since the owner, Don Ward, transplanted the notion from its original London base a year ago. "They're more up for it, here," Smart said after the show.

"The suggestions from the floor for what we should improvise round are more surreal and they are more open. In London it's more cynical, more 'Come on, you bastard, make me laugh'." Except when it comes to stand-ups. "There the Northern audience is much harder to please," says Don Ward. "It's interesting that you get a different audience for 'impro'. It's much more theatre-going than for the stand-ups." He's interested in such observations, partly because he needs to understand the variations on who'll go down better in each of his two venues, but also because he hopes that the Manchester Comedy Festival will become the UK equivalent of Montreal's "Just for Laughs" comedy festival.

Not that the comics want to make too much of the North-South comedy divide.

"In both places, when you ask for 'impro' ideas the audiences always come up immediately with the vibrator and toilet brush suggestions," says Tony Slattery. "We always say we won't do them. If an object has inherent comic value there's nowhere much you can go with it."

Nor is there much they seem to be able to do about the Manchester Comedy Store's other distinguishing feature – the constant interruption of the gags by members of the audience pushing through the stalls carrying massive trays crowded with pints of Boddingtons. For the drink, as Macbeth's porter might have noted, is a great provoker not just of laughter, but also of a steady stream of second-half visits to the lavatories. "They seem to have weaker bladders up here," says Andy Smart. Either that or, as someone with the logical acuity of Aristotle might have noted, they just drink a lot more. You gotta laugh, incha?