Ever since R.E.M. emerged from the collegiate wilds of Athens, Ga., in the early '80s, the American underground rock scene has been simply swamped with moody, melodic guitar bands. Corralling these groups under a workable catch phrase, however, is another matter entirely.

After a number of similar-sounding bands followed R.E.M. out of Georgia, it became tempting to term this the New Southern school of rock. But that geographical definition makes it difficult to deal with the fact that there are bands as interesting and original working this vein from New England, the Midwest and California.

Perhaps the real reason these bands seem so difficult to classify is that what is at work here isn't a matter of style so much as esthetic. In a sense, what these bands have developed is a sort of postpop music, self-consciously playing off the formal aspects of pop music. The approach isn't entirely unprecedented -- musically, its roots go back to the Beatles' "Revolver" and the Beach Boys' "Pet Sounds" -- but unlike the calculatedly commercial ploys of such pop formalists as Big Star or the Raspberries, the postpop bands make as much of their distance from the mainstream as they do of their fondness for traditional rock devices.

Take Dumptruck, appearing tonight at the 9:30 club. Although this Boston-based quartet appears to have no difficulty generating succinct, catchy melodies, those tuneful tidbits are almost never the focus of the songs on "Positively Dumptruck" (Big Time BTA 10011). Instead, they're treated almost as if they were just another part of the arrangement.

That's not to say the melodies don't sink in; indeed, such songs as "Back Where I Belong" and "Autumn Light" are utterly infectious. Where Dumptruck differs from the typical pop act, though, is that the band sells its sound and songs as a package, instead of splitting the elements into separate, interdependent components of a larger whole. Thus, the fuzz-tone guitar lead or clavinet bass line that crop up in "Back Where I Belong" end up sounding as important to the listener as the vocal line and lyrics.

Needless to say, this puts considerable pressure on the band to maintain an overall excellence few groups ever manage. Yet Dumptruck takes the challenge in stride. Much of that seems to stem from the close interplay between band members, for not only does the guitar work of Kirk Swan and Seth Tiven interlock as easily as their voices harmonize, but bassist Steve Michener and drummer Shawn Devlin complement each idea as if by telepathy.

A producer's role is crucial in managing the flow of instruments and ideas, and few have handled the responsibility as well or as eagerly as Mitch Easter. On "Run" (DB 79), the third album by the Windbreakers, Easter is entirely in his element. Although he shares the production credits with Tim Lee and Bobby Sutliff, the two actual Windbreakers, and studio sidekick Randy Everett, Easter seems to be the most influential.

Oddly enough, Easter's greatest strength is exactly the opposite of what is usually expected from a producer. Instead of focusing upon and highlighting the central melody of a song, his production ideas seem to run interference against it, effectively merging the melody into the overall sound. Thus, "This Time She Said" is larded with fat, feedback-drenched guitar, in part to add an edge to the music but as much to underplay the song's classic chord changes.

After all, it does take a certain amount of rock classicism to maintain the attention to form that postpop bands depend upon, and so it should hardly come as a surprise that the Windbreakers' strongest songs, in particular "Don't Wanna Know," owe much to the harmonic language of mid-'60s rock. At the same time, the band ends up sounding somewhat derivative, precisely because the Windbreakers are often too close to that idiom to achieve any real distance.

Maintaining a familiarity while at the same time avoiding that identity is a trick E*I*E*I*O is especially good at, for as "Land of Opportunity" (Frontier FLP 1017) plainly shows, this band's sound is as effective as it is eclectic.

"This Time," for instance, opens the album with a burst of Beatlesque harmony that's deliciously at odds with the dissonant drive of the guitars. It isn't that the band, which hails from the Milwaukee area, is incapable of constructing a simulacrum of Fab Four harmonies, but that the band prefers to keep the listener off balance by playing against those expectations.

Where E*I*E*I*O shines brightest, though, is through its interjection of country music mannerisms. "Me and Jesus Christ," for example, effectively parlays country gospel into hard rock without making the obvious connections that clutter the cowpunk movement, while "Hello Heartache" and "Every Word True" absorb country music's vocabulary so effectively that it almost seems unfair to mention it as an outside influence. "Land of Opportunity" is a wonderful piece of work, a wholly conceived musical vision that makes it one of the most exciting debuts of the year so far.