Like old soldiers, blues music never dies. It just seems to fade in and out of national prominence every decade or so.

As we move into the '80s, the blues is in the midst of a periodic hibernation. Between power pop, new wave and the remnants of disco, there is little space left on the charts for rhythm & blues, swing, country blues or any of the other direct offshoots of the blues. Even mainstream outfits like the J. Geils Band, which built rock reputations on time-tested R&B riffs, seem to have fallen from grace. So "Makin' Music" and "The Fabulous Thunderbirds" are two albums of blues-based music that have about as much chance of making the Top Ten as the Washington Capitals have of winning the Stanley Cup.

But the artists involved appear to have less ambitious aspirations: Gatemouth Brown, from New Orleans, and The Thunderbirds, from Austin, Tex., seem content to operate within the small-time confines to which their no-frills musical policy restricts them, while Roy Clark, of Nashville (and Las Vegas), has intentionally abandoned his Hee-Haw audience, at least temporarily, in order to make music, from which he will certainly derive more personal satisfaction than financial reward.

In an apparent effort to reintroduce his guitar as something other than a TV prop, Grammy-winner Clark has teamed up with 55-year-old Louisiana legend Clarence "Gatemouth" Brown and a host of diversified musicians to create one of 1979's most delightful surprises. Even the fact that Clark and Brown share the same management meaning that the concept for this album probably originated not with the artists but on hustlin' Jim Halsey's drawing board, fails to taint this musical marriage. "Makin' Music" cooks.

As one might suppose from the title, this is not a formal affair. Producer Steve Ripley has given the record the feel of a loose jam session, leaving in the whooping, exhorting and chatter of the studio. But he does not digress into sloppy cronyism, giving us only enough behind-the-scenes color to reveal that the band is having itself one whale of a fine time.

As of this writing, Brown has no doubt returned to New Orleans (one of the few cities in America where a blues artist can find a steady gig and an appreciative audience), while Clark has gone back to the business of being a TV personality with his reputation as a legitimate musician restored. But they managed to move out of their respective spheres long enough to create a timeless piece of music . . . "Makin' Music" is a minor classic.

The Fabulous Thunderbirds have no such coattails on which to ride into the national consciousness. Like several other white bands around the country (i.e. Roomfull of Blues, George Thorogood & the Destroyers, and D.C.'s own Nighthawks), the T-Birds have somehow become musical outcasts of their generation, forsaking the lure of rock 'n' roll in favor of genuine American blues. And the T-Birds go all the way: Aside from some of the decidedly rock flourishes that add spice to their semilegendary live performances, this quartet plays straight-arrow, down-in-the-mouth, funky blues. And the production of their debut LP, by Denny Bruce, does little to fluff up their sound. "The Fabulous Thunderbirds" is a spare, no-nonsense record, devoid of gimmickry and gadgetry.

Nearly every song fits neatly into a well-established blues category, with little difference in design or execution between the six original compositions (by vocalist and harmonica player Kim Wilson) and the five relatively obscure gems that the group covers. The only cut that might ring a bell is "Scratch My Back," the slinky, sexy Slim Harpo hit that was No. 1 on the R&B charts and slipped into the Top 20 on the Pop charts in 1966. Otherwise, the album manages to travel familiar terrain without rehashing worn out material.

The only problem with "The Fabulous Thunderbirds" is that it may be a little too hard-core, making no concessions to those who are not already hooked on unadulterated blues. The rhythm section (drummer Mike Buck and bassist Keith Ferguson) never stretches out, hitting a stride and holding it throughout each song, making Wilson and Vaughan struggle against the static to hold our interest. The T-Birds, to their credit, are not trying to be something they're not (i.e., black) but neither do they fully succeed in in conveying the immediacy of their personal blues passion or the sense of finger-snappin' style that pervades their live performances.

What albums like "Makin' Music" and "The Fabulous Thunderbirds" should do, besides entertain and move us, is to point us back to the original sources of this vital American music. Both these records are more legitimate and less exploitive than, say, The Blues Brothers, and they foster and uphold a blues tradition currently in a period of relative disfavor.