JAZZ THE CLOWN - Charles Mingus (Atlantic). If for nothing more than the title selection, this album is worth the purchase. The Clown, narrated by Jean Shepherd, is a weighty bit of moral philosophizing that should be required listening for anyone in show business or for anyone who contemplates such a career. Mingus, augmented by Curtis Porter, reeds; Jimmy Knepper, trombone; Wade Legge, piano; and Dannie Richmond, drums, also presents three other original jazz compositions in Haitian Fight Song, BIue Cee, and Reincarnation of a Love bird.