Pal Joey, a musical by Rodgers and Hart, adapted with a new book by Richard Greenberg. Roundabout Theatre Company at Studio 54. Starring Stockard Channing, Matthew Risch, and Martha Plimpton. This sparkling adaptation of the classic Rodgers and Hart musical "Pal Joey" starts off like a house on fire in the opening number choreographed by Graciela Daniele. Act I keeps up this pace, with one great standard following another, splendidly choreographed. At the intermission I was thinking that this is finally a musical at Studio 54 worthy of the wonderful revival of Cabaret. Like Cabaret, the sets and the work itself fit beautifully into the seedy, shabby theater. Unfortunately Act II is a bit of a letdown. Part of the problem is an added Rodgers and Hart number, "I Still Believe in You" not originally in "Pal Joey." As sung by the sweet pretty ingenue Jenny Fellner, playing Linda English, it stops the show dead in its tracks. It seems to go on forever and the lost momentum is never recovered. I don't think Greenberg's new book is an improvement over the original and the elimination of a Melba Snyder character who sang "Zip", in this revival giving the number to Gladys Bumps, superbly played by Martha Plimpton, is a mistake. Plimpton, displaying a sumptuous, smokey singing voice of near Jo Stafford-like quality, creates a believable floozy and is marvelous in "I'm A Red Hot Mama," but she is not suited to "Zip" and, in fact, her personification of Gladys as a bitter, over-the-hill bimbo actually robs the comic number of its, pardon the expression, zip. Stockard Channing is a fabulous Vera Simpson and she brings off her songs with aplomb although it must be said that she cannot make the magic with them that Vivienne Segal did - something that a Donna Murphy might have accomplished. Nevertheless it is Channing's show. And that is because the Joey, who is utterly believable in the part, lacks a certain "it," that requisite star power, and his dancing is only workmanlike. He's a plus, but he's not a star. This show is still a preview (although late in the preview run) and Matthew Risch, originally the understudy, is a promising work in progress. He may yet get that special insouciance and confidence which would make him into a star. As of now, Gene Kelly, or even Harold Lang, he is not. The production is sensational looking - late 1930's Chicago is onstage at Studio 54. With some more improvements this could be a Chicago-like hit. As it is, it's a very enjoyable 2 1/2 hours with some of the best Broadway music ever created, played by a first rate ensemble led by the legendary Paul Gemignani. We were "Bewitched" by the score. Broadway Bridge and Tunnel Test Grade B.