Country music devotees have been known to insist that country music is the only pure form of American music. They are chauvinistic about its authenticity and proprietary about the regions from which the music emanates. Part of their credo is "to sing country, you must be country."

Country purists would have no choice but to disown Gordon Lightfoot, Canadian-born, small-town bred and classically trained who studied orchestra in Los Angeles before becoming a recording artist in 1956. But, purists to the contrary, Lightfoot's country flavor has been unmistakable over 12 years and 14 albums.

Lighfoot's 15th album, "Endless Wire" (BSK 3149), sings of country concerns in country accents, at the same time venturing into and exploring a rock idiom on two of the 10 songs ("Endless Wire" and "Songs the Minstreal Sang"). That he is not completely fluent in this idiom is evident, but ironically, this attempt, albeit unsuccessful, rescues the album from behemoth banality.

The problem with most of the album is that it consists of Lightfoot rehashing the same melodies, harmonies and chord progressions: as predictable and uninspired as ever. Not only are the songs not particularly gripping, but Lightfoot's delivery is slick, his voice lacks conviction and he sounds immeasurably bored.

Only "if There's a Reason," a lover's lament over a broken relationship, approaches the simple poignancy so typical of lachrymose country songs. Here, Lightfoot's voice whines and weeps with the best of them.

"Endless Wire," the song for which the album is named, introduces a rock riff on the guitar similar to that used in "Judas' Death" of "Jesus Christ Superstar." One melodic phrase repeats itself four times, and then inverts and repeats another four times, giving a sence of endless circularity counterpointed against the urgency of the riff. The song then moves in another melodic direction, changes temp and becomes more ballad-like. The tension between the two sections is too great, and the song breaks down into two separate and alternating melodic lines, one engaging, the other irritating because it interrupts the progress of the first.

At his best (my choice is "Summer Side of Life," MS 2037) Lightfoot combines intriguing narrations an vignettes of country life with an infectious lyricism born of a country sensibility, of not a country background. The tunes are manifestly hummable, and though the subjects are often sad - loneliness, rejection, poverty - the melodies and treatments are far from blue. His music, instead, suggests affirmation and optimism (similar to John Denver's but without the saccharrin overtones.)

But affirmation demands involvement. On this album, Lightfoot sounds like a laid-back cowboy - he's always sounded that way - but so laid back and seemingly disinterested that one fears he may slip off his horse.