As Bruce Springsteen's ongoing tour proves, the blue-collar rock 'n' roll heroes of the late '70s and early '80s can still sell concert tickets to their baby-boomer fans even if they can't sell CDs. "John Mellencamp" suggests a reason why. The 47-year-old's first album of new material in five years is a perfectly respectable representation of the themes and the sound he has pursued for 20 years. The new disc contains some catchy sing-alongs ("Your Life Is Now" and "Miss Missy") and some brooding meditations ("Positively Crazy" and "Days of Farewell"), even if they're neither quite as contagious nor as penetrating as his best known songs.

Die-hard Mellencamp fans will buy the album and will probably be pleased with the subtle variations on his signature style. There's no reason for more casual fans to buy it, however, for it contains no song as irresistible as "Small Town" or "Jack and Diane" nor any dramatic departures from the past. As the opening lines of "Eden Is Burning" ("Diane and Jack went to the movies") suggest, this is the pop-music equivalent to the fourth or fifth sequel to the hit movie -- still good but not good enough.

Willie Nelson, who has released more than four albums for each of Mellencamp's, has given us a good reason to buy his latest. "Night and Day" is an all-instrumental project that forces us to confront the fact that Nelson is not only one of our finest singers, he's a hell of a guitarist, too. Nelson, who once inspired a Miles Davis composition, has a jazz-like sense of phrasing and harmony. He and his regular road band are joined by fiddler/mandolinist Johnny Gimble (an alumnus of Bob Wills' Texas Playboys) for an all-acoustic stroll through standards written by the likes of Cole Porter, Jerome Kern and Fats Waller. The group's elastic approach to the beat and lyrical grasp of melody is perhaps best exemplified on the version of Django Reinhardt's "Nuages."

Both appearing Sunday at the Nissan Pavilion in Farm Aid '99 along with Neil Young, Trisha Yearwood, Deana Carter, Steve Earle, the Dave Matthews Band, Barenaked Ladies, Sawyer Brown and Susan Tedeschi.

To hear a free Sound Bite from John Mellencamp, call Post-Haste at 202/334-9000 and press 8130. For a Sound Bite from Willie Nelson, press 8131. (Prince William residents, call 690-4110.)