The Big Chill, Eastnor Castle. Herefordshire

It could be the beginning of the end: the Big Chill has become a destination for themed stag parties. Like the corporate groups one sees in airport queues for Dublin and Prague, last weekend's "ambient" festival was full of cross-dressing men and African explorers in pith helmets, who looked to be having a great time. I know, it's all for a laugh or charity and you should just preserve that stoner's smile and grin benevolently at everyone who crosses your path, whatever they're wearing. But that's the trouble with the Big Chill: it makes you so, well, conflicted.

It could be the beginning of the end: the Big Chill has become a destination for themed stag parties. Like the corporate groups one sees in airport queues for Dublin and Prague, last weekend's "ambient" festival was full of cross-dressing men and African explorers in pith helmets, who looked to be having a great time. I know, it's all for a laugh or charity and you should just preserve that stoner's smile and grin benevolently at everyone who crosses your path, whatever they're wearing. But that's the trouble with the Big Chill: it makes you so, well, conflicted.

On the one hand, you want to have fun in the sunshine and frolic with a frisbee; on the other you fantasise about taking pot-shots at MCs who say, "Make some noise!" and, "Big it up!", or harbour murderous thoughts of wiping out whole columns of DJs. The sheer brainlessness of much of the entertainment is mind-boggling. A whole day can go by without anything appearing to happen at all, bar low-security knob-twiddling. Waiting for Talvin Singh to take the outdoor stage on Saturday night proved interminable. By the time he did arrive, it was freezing cold, the Indian classical music he played seemed too self-consciously austere, and your behind was sore. At such times, retiring to the Dance Tent is the soft option. Here, Mr Scruff demonstrated the art of playing records in public in a superb set that proved that, if the audience is stoned enough, absolutely any record in the world will sound good. This year, he chose to set himself a real test by slipping in The Cure. It sort of worked.

But perhaps you can't complain. The Big Chill does exactly what it says on the packet: it, like, chills. After a week of rain, the sun shone compliantly throughout, the historic deer-park site proved perfectly suitable for a second year running, and the atmosphere remained remarkably civilised.

Some of the best pleasures were the incidental ones. The look of delight on the face of a girl DJ in the Cocktail Bar tent as she exhorted the crowd to dance to Aretha Franklin's "Rock Steady". Or foraging for falafels and chai among the many-coloured stalls.

The real brain-food arrived on Sunday night. The performance of The Matthew Herbert Big Band was quite astonishing, bringing new, transfiguring life to a form long dead. The obvious gimmick - that Herbert samples and reconfigures the contributions of his 18 or so musicians, in real time - isn't really the point. It's the arrangements themselves: the big, brassy, unapologetic Gil-Evans-ness of it all, complete with parping bass-trombone lines that more than satisfied the Big Chillers' need for low-frequency pummelling. Dressed in tuxedos (Herbert wearing wellies with his), the musicians also supplied a much-needed touch of theatre; satire, even. When the leader handed out copies of the Daily Mail and the band members began to tear them up, it provoked a huge cheer. The rest of the show was completed on a stage ankle-deep in shredded newsprint about falling house prices.

Running partly concurrently with Matthew Herbert was Jaga Jazzist. A Norwegian 10-piece whose members double and even triple instruments to create an incredibly flexible unit, the band plays a blend of music that is entirely its own, mixing virtuoso solos (including bass clarinet) with complex ensemble arrangements. While there's a slight touch of prog rock in the compulsive time-changes, Jaga Jazzist is the best band I've seen all year. Real music may be catching up with the Big Chill aesthetic after all.