Liza Minnelli brought her 1979 "act" to the Kennedy Center Opera House for a six-day, eight-performance run that began last night. With only a few matinee seats left, it should make for another sellout on a tour that began earlier this month in New York. The evening is a generally successful mixture of Minnelli's showmanship and studied theatrics in a genial battle with a sterile ambience.

The Broadway element, represented by songwriters as illustrious as George and Ira Gershwin and as pedestrain as John Kander and Fred Ebb, wins out over the often unimaginative Las Vegas-style production. The Gershwin name crops up three times, from the exuberant opening, "How Long Has This Been Going On," to a credible and beautifully developed "The Man I Love" and a poignant "Someone to Watch Over Me." That's three winners and so what if Minnelli's strengths are less in her solid coloratura than in her superb phrasing and exquisite transitions.

A case in point in Charles Aznavour's ironic "Happy Anniversary," which is recited more than it is sung. Minnelli's subtle gestures of resignation ring true in a manner that she strives for but never attains in Kander's and Ebb's allegedly erotic "Arthur in the Afternoon."

Kander and Ebb, of course, wrote her Tony Award winner "The Act," and there are echoes from it in Minnelli's current show in songs like "City Lights" and the pair's theme to her ill-fated film, "New York, New York." There are also several throwaways in the two-hour show. But when Minnelli belts out a ballad -- and that's something that happens with regularity -- she can be truly mesmerizing.

A few mistakes mar the show -- Halston's uninspired wardrobe and some Las Vegas-lounge posturing by two dancers who sing a lot bettr than they dance. And both dance a lot better than Minnelli.

It's been almost 14 years since Minnelli's nightclub debut at the Shoreham Hotel. More than a few awards later, she represents a vanishing style of popular music that emphasizes production and individual charisma.

In the show's closing number, "Shine on Harvest Moon" Minnelli plays a strange trick. In an evening that has been a celebration of her own achievements, (yes, she does "Cabaret") she tousles her hair, surrounds her lanky, broad-shouldered frame with a '40s-sytle dress and suddenly looks like and recreates the unique, controlled gestures of her mother, Judy Garland. But she doesn't particularly try to sound like her, and that's the paradox and the shadow of Minnelli's performing life. It's a strangely defiant and triumphant note to end on.