I don't know about you, but I have no trouble at all placing Johnny Cash at the very highest level of 20th-century American popular music, right up there with Louis Armstrong, Woody Guthrie, James Brown, Frank Sinatra, Billie Holiday, Muddy Waters, Mahalia Jackson, and Chuck Berry. For me, the revelation was seeing him at the Cubby Bear last summer, where with a tight, tough four-piece band he demonstrated that the sinewy core of his art--the clear, uncluttered vision of "Hey Porter," "Folsom Prison Blues," and "I Walk the Line"--survives intact and unspoiled, despite the slick trappings with which his recordings have too often been oversweetened in recent years. Listening to Cash suggests that America may be more than just a den of xenophobic racists--it's also the Grand Canyon, the Mississippi River, and honest hardworking people stuck in a cycle of poverty, trying to find a way out. Cash's work is an oasis of historicity in a TV-addicted culture increasingly stuck in the eternal present; when you catch how his "Cry, Cry, Cry" reiterates the same themes and arguments articulated in some 16th-century Elizabethan sonnets, or how his "Five Feet High and Rising" respects timeless poetic principles, using clear, well-chosen word pictures to make us really see the floods that swept over the Arkansas farmland of his impoverished Roosevelt-era childhood, it reminds you that the past is parent to the present. All this, sung in a voice that ranks with Sinatra's in its artless inimitability--and set to a guitar accompaniment that almost anyone could play, really--is country music distilled into its most nourishing possible essence; it's not about cheatin' or drinkin' or any of that crap so much as it is about just maintaining your dignity in a world gone mad. June Carter Cash and the Carter Family--a country music institution in their own right--open this weekend's show. Friday, 7:30 and 10:30 PM, Cubby Bear, 1059 W. Addison; 327-1662 or 477-7469.