By RICK MITCHELL

From Boogie Nights and bell-bottoms to endless Brady Bunch reruns, the decade of the '70s is enjoying a nostalgic revival in popular culture.

But for many rock music fans, the '70s have never really gone away. Each summer, the concert tour schedule fills up with bands that became popular during that creatively fallow era between the hippie idealism of the '60s and the post-punk cynicism of the '80s.

Some of these acts haven't had a bona-fide hit in 15 or 20 years, yet they still outdraw many top-selling current artists on the so-called "shed circuit."

Witness this past weekend, when Saturday's bill of Stevie Nicks and Boz Scaggs and Friday's pairing of Chicago and Hall & Oates drew a combined 15,000 fans to the Woodlands Pavilion.

Saturday's show was the better-attended of the two (a rainstorm may have held down Friday's attendance), as well as the more interesting. Nicks is coming off a fabulously successful reunion with Fleetwood Mac, while Scaggs rarely tours anymore.

With Fleetwood Mac, Nicks' husky vocal tone offered a sweet-and-sour contrast to Christine McVie's taffylike smoothness, while her intuitive approach to songwriting balanced ex-husband Lindsay Buckingham's pop intellectualism and studio perfectionism.

Left to her own devises, however, Nicks' writing drifted off into a fantasy world that appeared increasingly irrelevant to the changes that have taken place in popular music in the past two decades. Street Angel, her last solo album before the Mac reunion, was not a major success.

While she can still pull off the "airy godmother" look in corsets and lace, age has not been kind to Nicks' voice, which has taken on a braying quality whenever it veers off-key, which is more often than one might wish.

Still, even a nonfan had to be impressed by the craft and vision that went into Nicks' show, as well as the reverence with which she was received by the audience. Her 100-minute set featured her biggest Fleetwood Mac and solo hits, as well as several lesser-known songs from her new three-disc career retrospective box, Enchanted.

She was backed by a studio-tight band led by her longtime musical director, guitarist Carlos Rios. The musicians had multiple opportunities to show off their chops during those interludes when Nicks left the stage to change from one long-sleeved lacy dress to another. (Apparently, Welsh witches, like Calvinist missionaries, don't believe in dressing down to beat the heat.)

An unplugged segment featured three songs inspired by Nicks' dreams- come-true career as a Hollywood pop star, including one written in 1965 when she was 17. Stand Back, an early '80s solo hit, rocked as hard as anything on the Mac's reunion tour, while Rhiannon opened with soft piano chords before kicking into the familiar guitar riff.

The show's emotional peak arrived on the acoustic Landslide, an old Fleetwood Mac tune. Nicks' voice conveyed a fragile balance of hurt and strength that touched a nerve in a way that mere nostalgia never can.

Scaggs' 50-minute opening set focused on music rather than flash. Although he's best-known for '70s pop-soul hits such as Low Down and Lido, his deepest roots are in '60s soul and blues-rock.

An extended version of Fenton Robinson's blues classic Somebody Loan Me a Dime allowed Scaggs, an underrated guitarist, to stretch out on lead. Better yet was I've Got Your Love, an original soul ballad from Scaggs' 1997 album Come on Home that would have sounded right at home on an Otis Redding album.

Vastly less impressive was Love, Look What You've Done to Me, a yukky ballad written for the soundtrack to the movie Urban Cowboy. We can only hope nostalgia for that unfortunate era isn't next on the retro- pop agenda.