There are at least three good things to be said about Liberace, and we might as well take care of them first.

He is not all that bad a pianist -- probably one of the top 10,000 in the United States, even with the severe handicap of wearing a half-dozen enormous rings while he plays.

He does not take himself too seriously, although he talks about practically nobody else.

Most important of all, he knows exactly what audiences want -- his audiences, at least -- and he gives it to them without considerations of musical quality or good taste.

What he gave last night at the Kennedy Center and will continue to give to full houses through Sunday is the lowest common denominator in American entertainment -- midway between hard-core pornography and grand opera, far from either but containing hints of both.

Contrary to popular mythology, the Kennedy Center last night was not awash in ladies with blue hair; the audience was a broad cross-section of Middle America, clad in everything from black tie to T-shirts and sandals, covering a spectrum of age and economic status that was limited only by the steep ticket prices.

Everybody loves Liberace. Or almost everybody. A small, determined group of animal rights protesters picketed at the entrance to the Kennedy Center, carrying signs that said "Fur Is Murder" and "Animals Are Not Fur Machines." They had selected a prime target; during a half-dozen costume changes, he displayed enough furs to populate a medium-sized zoo, purchased at a cost that would endow a small conservatory.

The most spectacular (though not the most expensive) was the one used for his first entrance, a massive creation in white virgin fox ("It takes one to know one," he said), with tails dangling everywhere and a long train. When he struck a pose with it wrapped around him, he looked, for a moment, remarkably like something from "Alice in Wonderland."

"Well, look me over," he told the audience. "I didn't get dressed like this to go unnoticed." He offered patrons in the first row a chance to take a quick touch, and several did so while he encouraged them: "Come on, there's plenty to go around . . . Take a fast look, because I'm taking it off. It's hotter than hell." Then he took it off and was transformed into a rock star or a very successful country singer.

Music is the least of the attractions at a Liberace performance. Anyone in Washington who wants to hear popular and light classical piano music played with style, imagination and flawless technique would do better to visit the Wintergarden Lounge at the Embassy Row Hotel, where John Eaton improvises nightly for the cost of a few drinks. His playing has Liberace totally outclassed. But a Liberace concert is an occasion wrapped in a mystique, and the music provides merely a background, a pretext for getting together to gawk at the furs, the glittery costumes, the candelabrum with its flickering electric bulbs.

It is an opportunity to watch the light reflected from a galaxy of rhinestones dancing on the walls. "If he twirled around in the spotlights, it would be like my senior prom," one member of the audience suggested. Later, while he was gushing about how he loved classical music, she quoted Oscar Wilde: "Each man kills the thing he loves."

But Liberace does not kill classical music. Mostly he ignores it, and at worst he inflicts upon it only superficial and momentary bruises from which it can soon recover. His Chopin medley had nothing to do, really, with classical music. It was, like all his programming, a medley of familiar tunes played with modest technique but a lot of simply achieved flash. The worst item on the program was an effort to recast "Mack the Knife" into the styles of Mozart, Debussy and Johann Strauss Jr. And it did no harm; it merely proved that this sinewy tune keeps its own character no matter how it is wrapped in any other style.

It might be argued that Liberace's appearance at the Kennedy Center will draw away money that might otherwise have been spent on concerts of good music. But an examination of the audience and its reactions makes that seem unlikely. Some of the money he will carry tearfully to his bank might have gone for video games, some of it for Geritol, and quite a bit for furs and jewelry (where it may go anyway). Very little of the money spent on Liberace could conceivably have been spent on the symphony or the opera; these things exist in a totally different world.

What Liberace stands for is not music but the right to be outrageous, to do flamboyantly mediocre things in public and be well paid for it. It was expressed most precisely, perhaps, in a number from "La Cage aux Folles" by his guest singer, Shani Wallis, who did little else worth noting and much to be deplored: "I am what I am . . . I am my own creation."

Whatever his musical endowments, he does know how to get an audience involved. Before his grand finale (in which "Chopsticks" modulated into a Hungarian rhapsody and then into the "Beer-Barrel Polka"), he had the audience singing along in "Let Me Call You Sweetheart" and "You Made Me Love You" while he glanced up from the keyboard to murmur, "Oooh, that's sexy." Then there was the almost-mandatory standing ovation, and the encore, in which he sang, "I'll Be Seeing You." He might be allowed to play the piano, but he should not sing that song; he should not sing anything in public. But nobody seemed to notice. Or, if they noticed, nobody cared.