An organ recital at the National Cathedral conjures up Bach preludes and fugues and hymns galore. Yesterday afternoon that aural stereotype was shattered by Raymond and Elizabeth Chenault, gifted duo organists affiliated with Atlanta's All Saints Church. Their program, which consisted exclusively of 19th- and 20th-century music, made the listener aware of the awesome diversity of both the repertoire and the instrument.

When employed to full effect, the organ is like a self-contained orchestra. In each of the five works performed on the Chenaults' program, myriad voices and tonal shadings emerged. Louis Vierne's "Carillon de Westminster," played by Elizabeth Chenault, takes the simple melody that we associate with church bells (and even doorbells) and weaves it through a musical landscape of oom-pah-pahs and razzle-dazzle chromatic figures. Arthur Wills' "Toccata for Two" creates a percussive morse code of chords and octaves, interspersed with repeated clarion calls. The Prelude on Sowerby's "Rosedale," a mystical impressionistic work composed and performed by Raymond Chenault, turns the organ into a reed section of oboes and bassoons.

There were times, however, when the diversity became eclectic gimmickry, and the power mere bombast. John Rutter's "Variations on an Easter Theme," receiving its world premiere here, veered from brash to medieval to jazzy to pompous. And at various intervals throughout the concert, this writer was reminded of those boisterous, declamatory movie scores penned by sci-fi fantasy maestro John Williams.