Reading Festival, Richfield Avenue, Reading

This year's Reading Festival starts slowly. But it provides constant examples of rock's continuing ability to exhilarate and surprise, bringing the major festival season to a satisfying end.

Friday night finishes with plain fare from Razorlight, but includes urgent moments from Maxïmo Park and Interpol, black-clad hits in the sunshine. Then on Saturday, a rock atmosphere starts to take hold. Panic! At The Disco, whose lead singer, Brendon Urie, was knocked out by a bottle from the crowd here last year, attract a few token missiles, mostly when they veer from polite hard rock into softer, more feminine songs. But they sound timid compared with reunited veterans Dinosaur Jr, whose J Mascis extracts liquid-silver streams of notes from his guitar.

Arcade Fire provide the weekend's first exhilarating moments. These religiously conflicted Canadian art-rockers play with a communal spirit reminiscent of African bands. When Régine Chassagne whips the stage with a towel, it feels like a tribal summoning of energy. On "Intervention", a church-organ sound combines with xylophones reminiscent of a Phil Spector Christmas single, as band-leader Win Butler lambasts religion, and, on "Windowsill", America too. It is wild, difficult music to excite a field full of people with, but they manage it.

Earlier, Bloc Party became the first of two bands heavily influenced by the equally difficult, cult post-punk band Gang of Four to prove a hit. Red Hot Chili Peppers are the second. Night falls as they arrive, allowing flame-red lights to play over the crowd, making this feel like the sort of old-fashioned rock show they describe on "By the Way". Their back-catalogue of hits is largely ignored, their crowning glory, "Under the Bridge", left unplayed. Instead, they try out Fleetwood Mac's "Songbird". Flea and John Frusciante play a soft, jazzy bass and guitar duet, before the drums smack into "Californication", while singer Anthony Kiedis largely takes a back seat. They find subtle funk corners to token old favourite "Give It Away", and close with a Miles Davis-style trumpet solo, and a dub instrumental. Defying the massive crowd's expectations and playing what they feel like wonderfully well, they disappoint many, but stay true to themselves.

Sunday is when Reading returns to its hard-rock roots on the main stage, where Nine Inch Nails's crackling, knife-sharp set is tremendous, Trent Reznor clearly revelling in the occasion. For those fleeing to quieter pleasures in the neighbouring tents, Cold War Kids' scratchy, chiming guitars and rolling early 1970s grooves are an early hit. Nathan Willett's high, clamouring voice gives them a welcome edge of hysteria. The crowd clap spontaneously to single "Hospital Beds", and a bigger stage beckons next year. Devendra Banhart follows, he and his hirsute musicians wearing straw boaters, like The Band on a day trip to Cambridge. But Banhart is soon topless, and, belying his reputation as a folk singer, playing Latin American street jams and 1960s LA acid rock. He even lets a girl from the crowd up to sing her own song. Though he seems a free, freaky figure, there is deceptively controlled intelligence behind his loose, inclusive, barrierless rock.

In the festival's closing hours, fires are started, and unconscious bodies lie scattered in the dark. Over all four stages, fine music can be heard. UK punks Gallows prove friendlier and more musical than their confrontational reputation would have you believe, while, in an impassably packed tent, Brazilian sex-funk stars CSS play L7's "Pretend We're Dead". In the next tent along, Seasick Steve, 2007's festival perennial, plays blunt blues, to a strong reaction.

The Smashing Pumpkins, dressed like extras from A Clockwork Orange, close the weekend with another set light on hits. They sound shaky, dour, too. But in a nearby tent, The Hold Steady are playing songs of small-town romance that might serve as a working definition of rock 'n' roll. It's a fine way to finish.