NEW YORK -- In the past decade, Radiohead have been called dour scientists who use the stage as a sonic laboratory. But during the first of their two shows at the Theater at Madison Square Garden, they were more like excited kids on a playground filled with exotic toys.

Singer Thom Yorke shook invisible maracas, twitched and talked into his guitar pickups as his bandmates wove a backdrop of skewed rhythms, unsettling noises and skittering electronic beats, which coalesced with Yorke's pained, elliptical vocals.

For some, this type of high art is sobering. For Radiohead, it's simply a blast. Clearly the bandmembers -- Yorke, guitarists Jonny Greenwood and Ed O'Brien, bassist Colin Greenwood and drummer Phil Selway -- are meticulous about writing songs, but playing them is another matter. During the show, they grinned constantly, gleefully conjuring dizzying arrays of sounds from their main instruments, as well as a variety of pianos, samplers, stage drums and an electronic gizmo that looked like an oversize PSP. Even Yorke was in a spiritually sound place.

"I'm gonna have to try out the drum set later," he quipped before the new song "Bangers 'N' Mash," then laughed as a small kit was placed to the side of his mic stand.

The older songs Radiohead played were culled predominantly from the angular electronic rock material of 2000's Kid A and 2001's Amnesiac, and they worked well alongside the seven new songs. Not that they're returning to the enigmatic drum-and-bass clatter of "Everything in Its Right Place" or "National Anthem" -- they're simply reclaiming their role as modern innovators after their somewhat lackluster 2003 disc, Hail to the Thief.

Four songs into the two-hour concert, Radiohead introduced fans to the first new number, "15 Step," which featured soulful vocals, a jittery beat, artificial handclaps and watery slivers of jazz guitar before launching into a combination of galactic keyboards and hiccupy guitar noises.

Two of new numbers rocked harder than anything Radiohead have done since OK Computer's "Paranoid Android." "Bodysnatchers" combined Yorke's trademark wail with the quirky dissonance of Sonic Youth and the drone of Velvet Underground, and the aforementioned "Bangers 'N' Mash" was a raw, propulsive audio melt of glam riffage, funk drumming and attitude that peaked with a dizzying pregnant pause before diving back into the melee.

The softer songs were equally captivating. During "Videotape," backward-sounding guitar gurgled through major, elegiac piano chords. Halfway in, an ominous beat cut through, and toward the end, O'Brien sat cross-legged twiddling the knobs of various effect pedals while Greenwood hunched over and sawed away at his guitar.

During "Arpeggi," a repeated three-note guitar arpeggio drove the rhythm while Yorke crooned. Sometimes it sounded like all the members were each playing a different song, but their parts intersected.

One of the many highlights, "Down Is the New Up," rode a sturdy backbeat over jagged riffs, mournful wails and soulful background vocals, pausing in the appropriate places for textural washes of piano and guitar effects. The only head-scratcher was "House of Cards," a hazy number that resembled a U2 ballad.

While the true excitement of the show came from the sneak preview of new songs, Radiohead also rolled out a cavalcade of hits. "Fake Plastic Trees" showed how organic and vulnerable the band can still sound, while "Street Spirit" and "Lucky" reminded the crowd that Radiohead were a killer mainstream alternative-rock band long before the arrival of Coldplay or Keane.

Near the end of the first encore, Radiohead performed the soaring, arresting title track from their 1995 disc, The Bends. They then moved into Kid A's "Everything in Its Right Place," during which the band built tension gradually over a bed of clicks and blips, then released it all at once in a flood of computerized noise and echoed vocals.

Before releasing Hail to the Thief, Radiohead embarked on a similar series of European and North American dates to road-test their new material. However, while that tour was more of a trial to separate the wheat from the chaff, this time, the band seems proud to exhibit the new songs with the knowledge that they're all winners. For this consistently challenging band, 2007 could be a banner year.

For more sights and stories from concerts around the country, check out MTV News Tour Reports.