THE BAD NEWS is that Saturday's PDQ Bach show at the Kennedy Center is being billed as the farewell appearance of the errant (and mythical) youngest son of Johann Sebastian Bach. Besides demanding tremendous creative and performing energy, this musical fiction, growing through the decades, must have generated some love-hate feelings in Peter Schickele, the hapless PDQ's "discoverer" and alter ego, whose serious music has been overshadowed by his comedies.

The good news is that there is enough PDQ Bach material on records to keep us laughing for a long time. The latest, the dramatic oratorio "Oedipus Tex," moves the Greek legend to Thebes Gulch, Tex., where the hero ("my friends just call me Ed") has a doomed romance with Billie Jo Casta, forgetting the cowboy principle that you should love your horse, not your mother.

The disc also features "Classical Rap" (a hip-hop monologue on the problems of yuppie life in Manhattan), an elaborate Birthday Ode for Johann Sebastian Bach with a lot of filial resentment between the lines, and "Knock, Knock," a cantata (sung by the Okay Chorale) whose text is based on some of the oldest jokes in the world.

PDQ BACH -- "Oedipus Tex" (Telarc). Appearing Saturday at the Kennedy Center Concert Hall.