The hoedown is almost as popular at Ford's Theatre as one-person pageants and gospel musicals and "The Robber Bridegroom," which opened yesterday afternoon there, does the do-si-dos as well as any show around these days.

"Bridegroom' is bright and light, and Mary Porter Hall's staging, reconstructed from Gerald Freedman's Broadway original, is occasionally downright dazzling in its inventive use of "story theater" techniques to tell an American tall tale.

Tall tales, however, can be used as palliatives as easily as they can be used as myths commenting on deep cultural currents. Alfred Uhry's musical serves the former purpose much more than did Eudora Welty's 1942 novella, on which it is based. Something has been lost.

Welty's story of a double-dealing gentleman-bandit along the Mississippi in the late 18th century is much spookier and richer than Uhry's knockabout, good-times song-and-dance routine. The sense of a wilderness was never far from the surface of Welty's story, but Uhry has set his show in a big barn and presented it as a recollection of those dark old days which are now safely behind us.

A couple of scenes imaginatively reproduce the forest, but they are not enough. The book's final scene's feeling of "civilization, at last," is missing.

Smiling young white folks fill the Ford's stage; there isn't a suggestion of the Indian "savages" who imparted a sinister subtext to the Welty tale. The deeper violence has been carefully excised from the musical, and the violence that remains seems literally slap-happy.

It's all in good fun. Maybe good fun is enough to expect out of a musical, but the residue of the darker substance lingers enough to raise annoying questions: Must we continue to find it amusing that the hero keeps punching out the heroine. That the ring of onlookers keps reminding the stepmother how ugly she is? Some of the laughter is exceedingly strained.

Thenagain, the lack of an intermission may have something to do with the feeling that the show goes on too long. The texture of the piece is so light and flat that an intermission could add a little artificial drama - given the absence of dynamics is Welty's originial.

Occasionally Uhry's simplification of the Welty narrative helps. Nothing is hard to follow, and the cast - with four of the Broadway leads - appears to know exactly what it's doing. And some of what it's doing requires a great deal of dexterity.

Tom Wopat's bridegroom is properly dashing and full-voiced. Rhonda Coullet, as the Cinderella he seeks, doesn't have quite enough of a voice, but she looks sensational and she mugs like Steve Martin in one light-headed moment of farce. Glynis Bell, as the stepmother, handles the stereo-types of her role with charm and humor.

Robert Waldman's country-flavored score begins on a high note as a couple of fiddlers stroll down the aisles. His ballads and quieter moments are generally more effective than the rowdier set pieces, the dancing occassionally seems superfluous.

But the less-stylized stage movement is ingenious indeed - American efficiency in action. This show stakes out a small, bright corner of Americana and doesn't ask any questions about the uncharted spaces.