For a bunch of guys who feel that advancing age should not deter them from doffing their shirts, the Red Hot Chili Peppers want you to take them very seriously. Not content with being the unofficial party hosts of the skate-punk generation, they want each new album to show off as much of their brains as they do their bodies -- to be seen as deep thinkers, despite their self-inflicted funk-punk-himbo image. The process reached a sensational peak on 1999's Californication, a high-water mark for a band that had been together about 15 years and had weathered enough highs and lows to fill a 12-hour episode of Behind the Music. With guitarist John Frusciante back in the fold after a harrowing bout with heroin addiction, the band came off like recovering frat boys seeking, and finding, some sort of spiritual awakening. They'd never sounded less mannered and more omnipotent.
The development continues on By the Way, which presents an even more refined version of the Chili Peppers. Gone for the most part are the kamikaze exercises in rubber-band gonzo funk, the insane-in-the-membrane jokiness, the boisterous, carnal drive. Anthony Kiedis -- who, like bassist Flea, hits the big four-o this year -- remains the king of the speed-freak lyric, but he works at being pensive and sincere, and the Chili Peppers as a band pursue more opulent, languid, and, for want of a better word, mature arrangements and textures. Producer Rick Rubin is back behind the boards, and the result is music that's more earnest and lofty than Californication, with a cushion of Beach Boys pop harmonies here, a somber string-section intro there.
The onset of this change was, of course, 1991's ''Under the Bridge,'' a song that presented their sensitive side with few apologies. New Age-y surf pop reminiscent of that song runs rampant on By the Way, and it's where the band shines best right now. The album's most memorable and beautiful moments come when the Chili Peppers settle into an airy groove and Kiedis sings sweetly. ''Dosed,'' a song of love and departure, and a seductively poppy come-on, ''The Zephyr Song,'' up the ante of Californication's mood pieces.
For every successful foray like those, there's a less satisfying track; the album is less focused and has a mushier center than Californication. The Chili Peppers dish out a wan power ballad (''I Could Die for You''), a cloying dose of flamenco rock (''Cabron''), and a tame version of their former badass selves (''Throw Away Your Television''). Grooves are replaced by stoner dub (''Don't Forget Me'') and rote ska-punk (''On Mercury''). The songs groove along pleasantly and have subtle hooks that come back to haunt you days later, but they lack the urgency of the band's best work.
Deciphering whatever big statement they're attempting to make is also no easy task. A few songs hint at serious issues -- a junkie's life in ''This Is the Place,'' a look at the grimier aspects of L.A. nightlife in the tub-thumping single ''By the Way'' -- yet the lyrics are frustratingly cryptic or offer no new insights. (The video for the latter, which resembles a lost episode of The Monkees, only muddies the waters.) Kiedis' scattershot approach to songwriting -- strings of non sequiturs that mix innuendos, double entendres, and beatnik jive -- hasn't hurt the Chili Peppers before: Is there any major rock band for whom lyrics have been more beside the point? But if they want to act like messengers for the New Somberness, they have to deliver a little more than lines like ''carry me down into the waters of love.''
At times, By the Way is more fascinating for what it symbolizes than what it is. As they near the 20-year mark that instantly classifies rock stars as institutions, the Chili Peppers have become a new breed of classic-rock band -- one whose roots lie in funk, punk, and old-school hip-hop rather than folk or blues. Countless lesser groups have taken a page or two from the Chili Peppers' notebook, and they may still: It's easy to imagine everyone from Fred Durst to Linkin Park examining the Chili Peppers' attempts to grow artistically while still adhering to their youth-rooted genres. No longer the most dangerous kids on the block, the Chili Peppers have settled for a less provocative fate: professional craftsmen, with or without their shirts.