The rock-and-roll stage comes in all shapes and sizes, but whether you’re talking about a smoke- and fire-belching Metallica rig or a postmodern playground like U2’s Pop Mart get-up, the goal at the top end of the concert business has always been to make the artist appear larger than life. In the days before giant video screens made the job easy, Kiss even went so far as to incorporate massive platform shoes into their costumes so that they could be larger — or, at least, taller — than life. Most artists on the arena level, however, rely on more sophisticated technologies to do the trick.

Radiohead, the enigmatic British band recently credited on the cover of Rolling Stone with destroying rock and roll, have put together a stylized and starkly skeletal stage for their first major tour since coming off the road in support of 1997’s OK Computer (Capitol) and embarking on the studio sessions that would yield a pensive, petulant, ultimately polarizing pair of CDs — last year’s Kid A and this year’s Amnesiac (both Capitol). When the band emerged (at 7:45 p.m. on the dot) a week ago Tuesday on the dusty and dusky horse-racing track at Suffolk Downs, daylight, yet to relinquish its grasp, muted the impact of the deep blues, crimsons, and violets that bathed the stage from strips of spots hung artfully above. But the menacing dark-gray cloud that hovered over the stage served as an equally powerful and oddly fitting backdrop for the stormy atmospheric rock Ed O’Brien and Jonny Greenwood began to sculpt with their guitars and the unsettled emotions singer Thom Yorke projected with his fractured verse and melancholy falsetto. Indeed, the cloud had positioned itself in such a way that the 25,000 fans milling the field — a number of whom were forced to beat a hasty retreat from the fried-dough and French-fry concessions ringing the track when Colin Greenwood dug into the familiar fuzztoned bass line of " National Anthem " — were left standing under open sky.

But as night descended and the band came into sharper focus, it became increasingly clear that, just as Kid A and Amnesiac turn the typical verse-chorus-verse structure of the pop song on its head, the touring set-up was designed to subvert the conventions of the rock-and-roll stage. Because rather than appearing larger than life, the band seemed dwarfed by the structure on which they stood and by the massive scope of everything from the sky above to the swarming crowd below. Even the two modestly proportioned, monochromatic video screens that flanked the stage like two flickering black-and-white television sets and carried impressionistic, cut-and-splice images of the action (or lack thereof) below only reinforced the fragile, human proportions of the band, particularly of the diminutive Yorke, who switched back and forth between guitar and piano and went from standing catatonically still one minute to shaking with the convulsive violence of a patient undergoing electroshock treatments as Colin Greenwood and drummer Phil Selway laid confidently into any of a number of the linear grooves that helped propel the two-hour set.

That sense of fragility complemented the choice of material, since the tour is dedicated to exploring the live possibilities of the studio-based experiments on Kid A and Amnesiac, both gloomy works steeped in alienation and paranoia. And the few tracks from OK Computer and 1995’s The Bends (Capitol) that rounded out the set — " Lucky, " " No Surprises, " " Street Spirit, " " The Tourist, " " Paranoid Android " — reflected the same state of mind. (As usual, the band avoided most of Pablo Honey, their 1993 debut, which featured the breakthrough single " Creep, " though that album’s " Lurgee " made it into the first encore.)

When you consider how small a role guitar plays on the two newest discs, Jonny Greenwood did an admirable job of finding ways to work in various abraded textures and the occasional stinging lead (though the big cathartic peaks came mainly from Yorke’s pained falsetto). But these days, anyone who comes to a Radiohead show expecting the kind of cheap thrills, big riffs, and easy pleasures that arena-rock bands usually deliver completely missed the point of Kid A and Amnesiac. One might have hoped for a little more intensity from a band who have done their best to strip their rock right down to its most naked emotions. But as a comment on the nature of celebrity in our media-saturated world, Radiohead’s performance drove home the message that Yorke’s been trying to get across for the past couple of albums — namely that the weight of stardom can leave the star feeling a whole lot smaller than life.