Like a fabled city, the new musical comedy "Timbuktu" keeps receding as you approach it. Originally scheduled to open Saturday at the Kennedy Center's Opera House, the black version of the 1963 hit "Kismet" has now moved the official opening date - the date on which it declares itself fit to be seen - to Jan. 14, although previews will be held from now until then.

The reason is apparent from its reception in Philadelphia, where it played before moving here yesterday. There, the director-choreographer, Geoffrey Holder, made a pre-curtain speech promising that the more than three-hour show would be drastically cut.

William B. Collins of the Philadelphia Inquirer called the book "dumb" and "a trashily romantic fable," the songs "drippy," and the dances "embelishments, rather as if Les Ballets Africains were trying to find a place to fit in and, not finding any, came on anyway."

The Evening Bulletin's Ernest Schier called it "heavy with low comedy, inspipid romance and a top-heavy physical production."

Nevertheless, we all love legends - "Timbuktu" is the Arabian legend transformed to 14th century Mali - and one of the powerful legends of the theater is that great Broadway successes can come out of pre-Broadway disasters.