By LYNN ELBER

LOS ANGELES (AP) -- There's a lull on the set of ``The X-Files,'' allowing star David Duchovny to smoothly demonstrate disco moves to ``Rock the Boat.'' Then he engages in a trivia battle to name the band responsible for the 1970s hit.

``Tell him what he's won,'' a playful Duchovny says in his best quiz show voice after a crew member comes up with the answer, the Hues Corporation. It's easy for Duchovny to be cheerful now that he is finally living and working in Southern California. But what about all those dedicated ``X-Files'' viewers who fret that moving the Fox drama from misty, mysterious Vancouver, British Columbia, will undercut its dark nature?

Give these fans alien invasions, government conspiracies and grisly things that go bump in the night. Don't subject them to lighthearted romps, especially bathed in sunshine.

The harsh reality: There will, unavoidably, be a brighter look as ``The X- Files'' returns at 9 p.m. EST Sunday for its sixth season. The first episode opens with a wink toward the series' new digs, says Chris Carter, its creator and executive producer.

`It's a shot in which we're looking at the sun, the bright, blazing sun, and we hold on it maybe longer than we should -- to make a point -- before we pan down to a desert which we'd never see in Vancouver,'' Carter says.

But before fans grab their sunglasses -- or the remote control -- Carter asks that they consider the value of a fresh approach. While Canada provided wonderfully dense, forbidding forests in which to track the bad guys, FBI agents Fox Mulder (Duchovny) and Dana Scully (Gillian Anderson) now are able to wander over new terrain.

``Like most problems, if you can figure out a way to turn them into virtues or an interesting solution, it's a good thing,'' Carter says. ``The only thing you can't get here is (visible) breath and the nice condensed windows. We can still do that, but it doesn't come free. When we need rain or fog or atmosphere, we'll do it.''

Locations used or planned for this season's shows include the Queen Mary, the grand old luxury ship anchored in nearby Long Beach; a decommissioned Air Force base; farm land, and even a spot that mimics Virginia.

On this day, filming is taking place in the Culver City High School gym, just a few miles from Twentieth Century Fox's lot on the westside. Mulder is crashing a class reunion dance -- hence the disco tune -- as part of a fraud investigation.

There are drawbacks to filming in the Los Angeles area, Carter acknowledges, such as higher labor costs and the time it takes to get around on the extensive, usually jammed freeway system.

The payoff, however, is happier actors. Duchovny lobbied for the Los Angeles move to be closer to his actress wife, Tea Leoni, and Anderson has endorsed the change despite her affection for Vancouver.

What else can Carter do to keep his stars content?

``We're writing good scripts. David is really excited, so is Gillian, and they're both extremely happy not to just be here but they think the work is really good this year,'' Carter says. ``That's all you can do for them, ultimately, is give them good material.''

The busy Carter is dividing his attention between ``The X-Files'' and his other Fox series, ``Millennium,'' which he is trying to nurture to story and ratings health. But Carter considers ``X-Files'' his ``first child'' and is writing and directing a number of episodes.

Duchovny also is taking the opportunity to write an episode and is slated to direct.

The season will include a continued emphasis on what Carter terms the show's ``mythology,'' Mulder's obsessive quest to solve his sister's long-ago abduction and uncover the intricate conspiracy he believes festers in government's dark corners.

But it won't be a one-note season, Carter promises.

`I think this year there are quite a few funnier stories in the beginning of the year .... before we come back to solid 'X-Files' scare,'' he says. ``We've done some stuff that made me laugh out loud this year.''

There's also an innovative approach in the episode shot aboard the Queen Mary: It was done in linear time, with every shot connecting to the next. Carter wrote and directed the hour in which Mulder and Scully appear to be caught in a Nazi-era time warp.

``I honestly think it's the best season so far,'' says the soft-spoken Carter.

He is confident the audience's enthusiasm will match his. He dismisses the low summer ratings earned by the series, blaming the numbers on the ready availability of the show in syndication and on videotape.

And he's convinced ``The X-Files'' movie, which did respectable box-office business this past summer, has the potential to bring in new viewers. For those who skipped the film, a recap of it and of last season's finale will smooth the way into Sunday's episode. There's something else to keep in mind, a plot twist that X-philes might find too bleak to ponder. Carter, Duchovny and Anderson are bound to the series for this season, and then just one more.

``That's gonna be the show. I think if it goes past that it will be great, but that's what I anticipate,'' Carter says.

Turns out there could be something worse than Los Angeles. Oblivion.

AP-NY-11-05-98 0145EST