Other stars whose record sales have been dropping include Mickey Gilley, who gained fame as co-owner of Gilley's, the Houston honky-tonk featured in the film ''Urban Cowboy''; Barbara Mandrell, one of country music's most recognizable faces, and the ''outlaw'' Waylon Jennings. And the list goes on and on.

This decline in sales, according to record industry observers, is not just a temporary trend but the end of an era. Nashville's music industry, diversifying into rock, pop and other idioms, remains healthy.

But the audience for the Nashville Sound -lovesick laments, tales of marital strife and other plain-spoken lyrics, sung with a rural twang, and often accompanied by arrangements more redolent of Las Vegas than of Southern cotton fields - is dwindling, growing old along with its favorite stars. Tales tell of concerts by country music stars where the entire audience was above 50 years of age.

The young audience that should be swelling the ranks of country music fans is looking elsewhere. Most rural and small-town youngsters now grow up listening to rock-and-roll. Most radio stations now play the same rock records, in rural areas as well as towns and cities. And the performers with country roots whose record sales remain healthy are mostly rockers with a country tinge - Hank Williams Jr. and the four-man band Alabama, for example. These artists appeal to an audience that is growing larger and getting younger.

Lure of Frontier America

The United States as a whole seems to be in the grip of a new romantic infatuation with the old West and frontier America, a trend that is evident in the recent commercial success of western fiction and Hollywood's rediscovery of the western movie. But Nashville's production-line country music is too slick and pop oriented to appeal to frontier nostalgia.

Among country artists, this movement's chief beneficiaries are what is known as the ''new traditionalists'' such as Ricky Skaggs and George Strait, who are going back to the roots of country music for inspiration, and making simple, soulful records without the strings and vocal choruses and other commercial clutter so typical of today's Nashville Sound.