By now we know that the Off the Circle Theatre Company is onto a good thing with its cabaret concerts showcasing various American composers. But it wouldn't take all that much to make a good thing better. So why are we still waiting?

Take "Waltz in Swingtime," the latest in the series, which features the miraculous output of Jerome Kern. Here are some of the sweetest melodies ever written for the Broadway stage and the Hollywood screen: "All the Things You Are," "They Didn't Believe Me," "The Song is You," "Pick Yourself Up" and "Smoke Gets in Your Eyes," just to skim the surface.

Granted, the Kennedy Center recently treated us to the majestic delights of Kern's "Show Boat," but the Off the Circle company has something else to offer--young performers singing their hearts out in the cozy atmosphere of d.c. space. No barriers here--audience and show are very nearly one. That much is dandy.

At the same time, the Off the Circle revues have become increasingly formulaic of late. They usually open with an ensemble number, then the performers trade off songs for the next 90 minutes before a final ensemble number. Interwoven are bits and pieces of the composer's biography, perhaps, but otherwise the material is really not shaped in any distinctive way. While the shows, this one included, are strongest when the full company is singing in harmony, those moments are all too rare.

Although "Waltz in Swingtime" comes up with one interesting pairing--Francie Glick, singing "The Last Time I Saw Paris," while Duncan Hollomon takes on "Long Ago and Far Away"--it is mostly content to present Kern's songs sequentially. Clustering some more of them together in medleys wouldn't hurt at all. Nobody's asking for production numbers, but a spot of invention on director Frederic Lee's part wouldn't harm things, either.

The "Swingtime" chores are evenly divided among Glick, Hollomon, Bailey Saul and Gretchen Weihe. Glick, who bears a certain resemblance to Bette Midler, can't deliver the romantic charge many of her songs require, and Saul tends to assert himself beyond the limits of his musical gifts. Hollomon, however, manages full-voiced renditions of "Where's the Mate for Me?" and "The Folks Who Live on the Hill."

But it is largely Weihe who keeps this evening afloat. A blonde, blue-eyed incarnation of what Hollywood used to call the girl next door, she is pert and unaffected. Her rendition of "Look for the Silver Lining" is sweetly plaintive, and the fresh innocence she brings to "Bill" makes that smoky ballad from "Show Boat" unexpectedly tender.

Still, if the Off the Circle company is not to dig itself into a rut, a little more thought has to go into the compilation of these revues. Pleasant they are. Wonderful they could be.

WALTZ IN SWINGTIME. Music by Jerome Kern. Directed by Frederic Lee; musical direction, Emily Bell. With Francie Glick, Duncan Hollomon, Bailey Saul and Gretchen Weihe. At d.c. space through June 11.