Sum of its parts

An ELECTRIC drone wafted through the air before Radiohead took the stage Sunday at the Hollywood Bowl. It was the ideal sonic prologue to the beloved English group’s latest Los Angeles appearance. Atonal and abstract, the drone invoked contemporary classical music, just as the curtain of long tubes encircling the band’s equipment suggested the churchy majesty of a pipe organ. But the fuzzy sound also had an edge, hinting at guitar freakouts to come.

This is the tension Radiohead rides, especially in its celebrated live shows: The sound it creates onstage is serious and complex, but it also delivers the whomp of more conventional rock. At the Bowl, beginning a two-night stand signaling the end of a long summer of touring and festival dates, Radiohead was completely comfortable flexing both aspects of its muscle. Its 25-song set enraptured its acolytes while exposing the contradictory desires this band stimulates: for live music as a once-in-a-lifetime experience, and for rock as ritual, providing dependable release.

Grinning and waving as they took the stage, singer Thom Yorke and his mates looked ready to relax and stretch out, but the twitchy, mutant rhythms of “15 Step,” from the 2007 album “In Rainbows,” recalled that for Radiohead, every stretch demands an equal contraction. Yorke jerked back and forth doing what some fans call his “psycho bunny dance” as the song unfolded, each element sharp-edged yet precisely aligned.

Radiohead’s sound relies on each player’s careful execution of a distinct line or rhythmic sequence that interlocks with every other part. It’s a structure more common in classical music and jazz than in rock, in which one riff or chord sequence is usually pushed to the forefront. (Dance music, a big Radiohead influence, is also based in pattern-making.) There’s a lot to hear in most Radiohead songs; that’s one reason they can sometimes feel vague.

Live, the band’s commitment to complexity is embodied by frenetic multi-instrumentalist Jonny Greenwood, who leapt from guitar to drum to keyboards to various effects boxes Sunday as the set progressed. Greenwood, who’s also becoming known as an orchestral composer, represents the band’s artiest ambitions. Whether bowing his guitar on “Pyramid Song” or triggering shards of sampled dialogue on “The National Anthem,” he fulfilled his role as the group’s ultimate music geek.

If Greenwood represents Radiohead’s flowering as an art project, Yorke brings the band drama. Self-effacing and serious in civilian life, onstage he’s a natural, if high-strung, showman. As a songwriter, he specializes in emotional extremes -- the almost altered states that arise internally when ordinary folk face mortality, wrestle with unresolved desires or allow frustration to go too far.

“I’m an animal trapped in your parked car,” he sang in “All I Need,” his kind of love song. Yorke’s back was to the crowd as he played piano, and he brought his careening tenor to a murmur; yet he still came across as intense. Like many initially awkward performers who’ve mellowed in time, Yorke has found a way to reconcile his dislike of rock-star poses with his impulse to put on a show. His awkwardness now seems reflective of the human condition, not just eccentricity.

The band’s other members provide crucial support -- not an easy labor in this ambitious group. The rhythm section of Colin Greenwood on bass and Phil Selway on drums interact with the music’s electronic rhythms in ways that enhance and expand upon them. On guitar and effects pedals, Ed O’Brien was not just Greenwood’s able second, he provided some of the basic elements that connect Radiohead to traditional rock.

Sunday’s set included enough older songs to show how much the band’s template has changed since early albums like “OK Computer.” The 1997 hit “Paranoid Android,” performed as part of the encore, is a multi-part song suite that’s challenging to execute, but it does provide a conventional climax and some rousing chances to sing along. Songs from “In Rainbows” proved catchy but not as cathartic, getting people dancing but earning fewer passionate cheers.

Pushing its audience to listen in new ways, Radiohead has earned its reputation as one of the era’s great live acts. But that old craving for songs with big hooks and stomping choruses lingers, and the band is smart to serve it too. That pipe-organ set turned out to be the background for a very impressive arena-rock light show; several Beatles-esque riffs and soulful melodies made it into the mix too.

And you know what? There was still plenty of room for drone.

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ann.powers@latimes.com