IN NASHVILLE they say the perfect country song would begin: "My mother's doing time 'n' my wife's two-timin' and I'm so drunk I fell off the train."

Actually, that's better than most. Contemporary country music has quite literally written itself into a corner. String arrangements and overdubs aside, country music hasn't changed in 40 years. Men still wash their hearts out with whiskey while their wives keep the Alka-Seltzer burning.

This same kneejerk emotionalism means that anyone who isn't completely tone-deaf can be a country singer. The pathos, the drama, the love, the suffering are written right in: No interpretation is necessary. And by the time the Clone Arranger has worked his miracle, the singer is superfluous.

Terri Gibbs, who'll be appearing Saturday at the Burtonsville Lions Club with Charley Pride, has a perfectly pleasant voice, deep and masculine and right on key, and completely without character. Unfortunately, the songs on "Some Days It Rains All Night Long" (MCA-5315) don't give her any help. "Sometimes I know how the melody goes, but I don't know the words to the song," she muses. "Some days go by, not a cloud in the sky, some days it rains . . ." blank, blank, blank. You too can write a country hit.

Gibbs only rises out of this lackadaisical la-la for her own composition, "Go Somewhere and Hide," which has a little more rhythm & blues sway to it, but even that is cripplingly understated. This is pre-packaged Muzak, no machinery needed.

Juice Newton, whose last plastic country-rock album yielded two made-for-radio hits, has collected 10 more synthetic sentiments for "Quiet Lies" (Capitol/EMI ST-12210) and, in her reedy, supporting-actress soprano, gives them just what they deserve.

"Heart of the Night," which is absolutely not to be confused with the Poco hit, has mind-boggling lyrics--somehow evocative of Karla Bonoff prostrate in Asbury Park: "Dark city streets twist and moan in the heat/As the night descends." Some are merely mindless, like the already successful and relentlessly bouncy "Love's Been a Little Bit Hard on Me." Some are unspeakably significant:

I said "You've got Hemingway's eyes"

And that night I called him "Papa"

Seems that there's so many lovers

Who'll hold you and yet

Whose names you forget.

Papa would have wanted it that way.

Terry Gregory, a Takoma Park photogene with well-scrubbed skin and a voice to match, comes over "From the Heart" (Handshake Records, FW 37097) like the original-image Olivia Newton-John. Not only does she look and sound the part, she's even hooked up with N-J's onetime mentor, publishing capo Al Gallico; every track on the album is drawn from the Gallico group.

Whomever these little ditties may eventually enrich, it's probably not Gregory. Like Newton and Gibbs, she's the victim of her material. "Stand By Your Man" is the "Star-Spangled Banner" of country torchers--a melody so ranging and so patently histrionic that it demands a hard intelligence as well as talent. Gregory's sweet-tempered rendition is like Pat Boone's singing Puccini.

There may be a clue to these albums' pea-pod predictability in the fact that they draw from the same stable of studio musicians; two of them, piano great Hargus (Pig) Robbins and utility infielder Terry McMillan, appear not only on Gibbs' and Gregory's albums but on Lacy J. Dalton's "16th Avenue" (Columbia 37975) as well.

This is as close to the real McCoy as you can get without first-rate material. First of all, Dalton's album (her fourth) is a real Billy Sherrill production, while the other three are just imitations. And second, Dalton has A Voice, a completely individual, straightforward, sometimes cracking, more-expressive-than-a-locomotive Voice.

She can twist it to almost any style, and one of "16th Avenue's" shortcomings may be that it ranges too far. There's a little folk-rock, a little blues, a little swing, a little blue-eyed reggae and any number of other dabs on this album, all artificially flavored but harmless. But even though Dalton co-wrote half the tracks, the songs aren't up to snuff. The best is probably "Jamaica," an infectious ode to love-in-the-surf fantasies.

There are 8 million albums in the Music City, and these are just four of them.