The word rehearsal doesn't really convey what happens when the members of Oasis get together to run through some songs. They are not, by temperament, men of moderation. While you can imagine Sting, for instance, shushing his session cats and suggesting that it might sound delightful to garland "Message in a Bottle" with a tin whistle, the Manchester quintet that utterly dominated the British rock scene in the nineties have a much less subtle approach to the concept of practice: They just get up onstage and clobber you. Even though Noel and Liam Gallagher, along with their bandmates and their touring crew, are alone this July afternoon in a cavernous, black-curtained studio in a strip-mally area of West London that looks more like Phoenix, they perform one heaving anthem after another—"Champagne Supernova," "Supersonic," "Wonderwall," "Cigarettes & Alcohol," "Morning Glory"—as if they're staring down a million drunken followers on a fog-shrouded moor as the sun rises over a mythical rock festival.

They are ridiculously loud. When Noel, who at 41 still sports a George Harrison mop top, picks up and starts to noodle away on his cherry-red 1960 Gibson 355—a six-string that he mentions is worth about $20,000—the first few notes actually stab you in the face. There have been rehearsals in the past where the sound level was so high it affected not only the band members' hearing but their vision. "I nearly wept with the volume," Noel says, grinning. "It was like standing in an onion shop." Liam, who at 36 has abandoned neither his famous Brian Jones bowl cut nor that alpha-orangutan habit of swaying his arms when he walks, doesn't evince any difference between singing in a stadium and singing in an empty room. He still wraps his hands behind his back as though he's been handcuffed, leans toward the mike with a glare that suggests a familiarity with the etiquette of pub brawls, and unleashes a sound that's somewhere between an Italian aria and a sneer. When he's done, he steps down from the stage, swaggers over to the catering table for a banana, and says, "Told ya."

Even the Gallaghers' mistakes are huge. Not long after they've thundered through the self-fulfilling prophecy of "Rock 'n' Roll Star," a dinosaur-size, distortion-drizzled pop blasts across the room and makes everyone duck and wince. It's not a nice noise. It sounds as though a Marshall stack just lost a game of Russian roulette, and a roadie sets out to repair what looks like a minor power outage. "Well, there's no point in our soldiering on until he's got it fixed," Noel murmurs. "Bet this doesn't fuckin' happen to U2."