The bells! The bells!

Phil Johnson hears house music with a difference at the Salisbury Festival from, among others, Robert Fripp, left

In Salisbury library, the fiction stacks on the ground floor are intersected by the bulbous white cabinets of old, streamlined refrigerators. Pull downwards on the chrome handles and the doors open to reveal the surprising contents inside: plastic dinosaurs on skateboards; a ship's lavatory complete with the sound of tape-recorded seagulls; a fridge inside a fridge; a hall of mirrors; a puppet show. No one seems to take a blind bit of notice of them. Pensioners carry their Jack Higgins or Barbara Cartland to the issue desk, and swotting students come and go, too busy for the delights of Les Frigos, an installation by French artists Opus. Perhaps they've already had their fill as the fridges are now into their second week, the dinosaurs approaching their best-by date.

But on the grand green of the cathedral - which for many is Salisbury, more or less - the studied nonchalance of the natives and the daily tour- bus quota of continental visitors is hardly less notable. In a fenced- off space adjoining the cathedral, Station House Opera are in the middle of a technical rehearsal. It isn't possible to ignore them - after all, there's 10,000 whopping great breeze-blocks piled high to form the stage- set for their symbolic re-enactment of the building of the cathedral, and weird, unearthly sounds are emerging from the speakers - but there's barely a rubber-necking passer-by to be seen.

The sculptures by Elizabeth Frink that are dotted about the green attract a little more interest, and their giant genitals have provoked a moral panic of sorts over the preceding weeks, with sundry nuns, official cathedral guides and the over-cloistered inhabitants of the close evidently scandalised by the faithfully rendered cocks and balls. June Osborne, canon treasurer of the cathedral, has gallantly held her own end up, defending the Michelangelo- esque accuracy of the bronze bits, though in a scheduled address to the schoolchildren of Marlborough College, she could get no nearer to the nub of the matter than a reference to "thighs". As has been widely reported, local kids have been less circumspect, using cover of darkness to decorate the figures with condoms and nappies, though now they are in their natural state once again, as photographers wait patiently for a mouth-agape nun to enter the frame.

Within a minute of entering the office of festival director Helen Marriage, outrage rears its ugly head once again, perfectly on cue. It's a thundering phone-call from Sir Edward Heath, the cathedral close's most famous resident, complaining about parking restrictions to be enforced by today's closing fireworks concert on the green, given by the Bournemouth Symphony Orchestra. Sir Ted is upset that "his people" will be inconvenienced. Marriage thinks that perhaps he would have liked to conduct the concert himself, though he gets his go at Delius in the cathedral next month. There's already been an irate call that morning from a local Freemason, angry at Marriage's accusation in the Daily Telegraph that the men-in-pinnies are responsible for putting a stop to a proposed rock concert that was to have happened at a far-away airfield. If only she hadn't chosen the Telegraph, you feel, the Masons would never have noticed.

In the cathedral itself, technicians are setting up the equipment for a sound installation by the guitarist Robert Fripp, who is something of a local celeb, living nearby with his wife Toyah Wilcox. This has attracted a clearly identifiable audience of outsiders, a bright splurge of ethnic trouser-problems clashing with the school uniforms of children with worksheets, the turquoise-jacketed official tour-guides, the black-surpliced verger- cum-security men and the armies of baggy French kiddies that together make up an average afternoon's cathedral population.

When, at 2.30pm, Fripp arrives and plugs himself in, the audience sits obediently at his feet like medieval pilgrims anticipating a glimpse of the true cross. When, after a minute or so, Fripp gets up again and walks around the nave to inspect the sound, which, of course, continues without him - the audience looks slightly alarmed. At length, Fripp - who looks remarkably like a 19th-century curate himself - returns to his guitar and the pilgrims are happy once again. It's a wonderfully successful experiment, the music as delicate as a glass harmonica, with ambient wisps of sound echoing through the cathedral in chorus-effects of bells and voices. We sit and listen in silent communion, as schoolkids try to measure the height of columns and solemn vergers patrol the aisles, hands held behind their backs, black skirts trailing.

Fripp continues for two and a half hours, in the first of what will be four afternoons' work. At Islington's Union Chapel last Saturday - from where many of the faithful have followed him - he did a stretch of eight hours without a break until the crew felt guilty - so a technician tells me - at nipping off to eat their sandwiches. The sound is designed for a four-way quadrophonic mix over six speakers and, as the performance goes on, it seems to develop a life of its own, the whole building resonating with oohs, aahs and bleeps as Fripp adds layer upon layer of fresh textures, like a sonic plasterer artexing the cathedral's ceiling.

There may have been some symbolic artexing at the grand opening performance of Station House Opera on Wednesday night, but it was difficult to be sure. Indeed, exactly what was going on - never mind what it meant - remained a mystery for most of us. On paper, the continuous construction of a building with breeze-blocks might not sound like much in the way of a performance, but the idea was infinitely more entertaining than the actual event. A group of men and women dressed in vaguely medieval costumes heaved the blocks about jauntily, but they mainly seemed to be moving the same blocks from one place to another, and it was very hard work. A rock band and a choir accompanied the action, such as it was, but it took such a long time to move the blocks that the music would run out while the work continued. At one point, someone high up in the structure seemed to be shouting "Over and over again" over and over again, but I couldn't swear to it.

The edifice itself was spectacular but it seemed perilously close to being jerry-built and occasionally blocks would crash to the ground and the operatives jump back in alarm. With no hard hats or safety footwear (for the performers, never mind the audience), one's natural concern was more for health and safety than art. All in all, it was just like having the builders in, and it seemed as if the work would never be finished; they were still hard at it when I left for last orders at a quarter to 11. Walking back through the cathedral close, I imagined I could hear Sir Edward Heath banging his head against the wall, over and over again.

`Les Frigos' 9.30am-4pm, Salisbury Library; festival ends today