Pop: Sonic Youth, The Forum, London

When Sonic Youth come to town, you discover who your friends are. As you try to get someone to accompany you to the band's first London show in three years, you realise that everybody is either washing their hair, mucking out the budgie or flossing their toes. You can sympathise. At the end of last Wednesday's show, you expected to be handed a certificate - "I survived Sonic Youth," perhaps. It wasn't so much a gig as an art exhibition with guitar feedback.

And still there was something mad and amorphous about the performance that you would have been sad to have missed. Sonic Youth are a self consciously avant-garde force whose songs can often resemble those wretched Magic Eye puzzle pictures: you either see the point or you don't. You could defend their worst excesses as theme music for acid trips, which is a bit of a cop out, because anything sounds good on drugs, except Tanita Tikaram.

The slow-burning thrill of Sonic Youth's music actually hinges on something quite rudimentary that you don't have to be out of your tree to appreciate - struggle. Between Kim Gordon's dry, dusty tones, and the gasping enthusiasm and boyish hurt of Thurston Moore, who shares vocal and guitar duties with her; between gentle melody and eardrum-obliterating noise; and between the thoughts in your head, which can switch from "this is heaven" to "I want to go home now please" in the space of a minute.

There was no such contradictions when the ethereal intro to the band's - and one of pop music's - finest anthems, "Teenage Riot", throbbed over the PA, and every heart in the room swelled and swooned inside its rib cage. Then Moore's scratchy riff kicked in, driven by Steve Shelley's urgent drumming, and suddenly you were 14 again (which was fine until you remembered that you'd brought the car).

Things can't get any better than that, you thought. And they didn't. But it was worth sticking around just the same, for the short, sharp shocks of "Junkie's Promise" and "Becuz", where Gordon, Moore and bassist Lee Ranaldo lined up, guitars cocked, as though they were about to start a 400m sprint. Conversely, "Washing Machine" and "Sugar Kane" had all the momentum of a marathon for slugs. But they made it around the block in the end, through the wilderness of some free-form jamming, and there was something both excruciating and satisfying about that circularity. Moore clearly agreed. "Sometimes my guitar goes so out of tune and it sounds so good that I just can't stand it," he grinned after some especially torturous feedback that had left him clutching his guitar like a banjo, and the rest of us clutching our ears.

"Long is the way/ And hard, that out of Hell leads up to light," Milton once wrote about Sonic Youth. And he was right: they make you realise just how long and hard the path actually is. But better yet, just how bright the light can be.