One of the oddest ideas to have emerged in the wake of the new wave is the notion that amateurism is preferable to expertise. It's not too difficult to figure out how this concept came into play; after all, didn't punk postulate a brave new do-it-yourself world, arguing that anyone could be a rock musician?

But what started out as a reaction against the vapid professionalism of mid-'70s arena rock soon became a law unto itself. Ragged rhythms, murky mixes and sour singing went from being a badge of courage to becoming an expected part of the esthetic.

Which was fine for those bands willing to take a stand on the fringes of accessibility, but it didn't leave much room for any erstwhile melodists who wanted to remain outside the mainstream. Practically the only ploy available was the raw-edged new wave folk sound disseminated by Postcard Records, a small Scottish label that recorded such bands as Orange Juice, Aztec Camera and the Go-Betweens.

These days, Orange Juice no longer exists, while Aztec Camera has fallen into a period of inactivity; only the Go-Betweens, a quartet from Brisbane, Australia, remain active today. But as the band's fourth album, "Liberty Belle and the Black Diamond Express" (Big Time 10030-1) shows, the Go-Betweens have learned a lot about how to make melodic strength work against musical weaknesses.

For instance, there's the matter of the band's vocals. Neither Robert Forster nor Grant McLennan is blessed with an especially supple voice, which means that the melodies they sing must be either very simple or heavily supported by the arrangements.

On the best songs, the Go-Betweens play off simple, singsong vocal lines against sturdy, tuneful arrangements. "The Wrong Road," a wistful waltz, is a typical example, with the first part of the verse shoring up the singer's pitch with a guitar line while the second part limits the vocalist to two notes, with a string section providing the secondary melody. As a performance, it's elementary but ingenious, holding the listener's attention despite its occasional inadequacies.

As a result, "Liberty Belle" manages to be far more than the sum of its parts. "Apology Accepted" seems on the surface to be just another Neil Young-style country rocker, but it takes on an additional tension thanks to the tightly coiled performance; similarly, "In the Core of the Flame" modulates wonderfully between anxiety and desire almost because of the singer's wandering pitch.

Not that every singer in the pop underground has pitch problems. Cathal Coughlan, who sings with the Irish quartet Microdisney under the name Blah Blah, hits every note square and sure, no matter where it falls in his register. Still, "The Clock Comes Down the Stairs" (Big Time 10012-1), Microdisney's debut, exhibits the same musical instincts the Go-Betweens display, from inventive arrangements to terrific tunes.

If anything, the songs here are even sharper than those on "Liberty Belle." Part of that is simply a matter of Coughlan's razor wit. "Past," for instance, mocks Britain with the chorus: "Who won the war? Who ruled the world?/ Who showed them all? Well, who cares?"

Mostly, though, it's the way the group expands upon its melodies that makes this album so captivating. Some of the touches are quite subtle, like the "doot-doot" harmony vocals behind the chorus to "Genius"; others are more elaborate, like the country rock breakdown that concludes "Goodbye It's 1987." In all, the arrangements don't just shore up the songs, but amplify their strong points, adding a sense of scale to each verse and chorus.

As such, Microdisney comes across like Prefab Sprout without the studio gloss, a deficiency that's more than made up for by the music's melodic integrity. This, after all, is a band that lives and dies by its songs, not its sound, and "The Clock Comes Down the Stairs" is proof that Microdisney's time has come.

Still, there's nothing wrong with building a band around a sound. Take the Cocteau Twins, an English duo whose latest album, "Victorialand" (4AD CAD 602), is so intensely atmospheric that its melodic content seems almost to melt into a haze of guitar and synthesizer.

A good bit of that derives from the dreamlike quality of the songs here. Unlike the band's previous efforts, "Victorialand" was recorded without drums or rhythm machines, relying for its momentum on Robin Guthrie's guitars and Elizabeth Fraser's skittering vocal phrases.

In lesser hands, that would be maddeningly soporific, but the Cocteaus infuse their songs with an infectious combination of innocence and calm. Granted, it's often difficult to tell what Fraser is singing about -- or, in the case of "Of April and May," what language she's doing it in -- but there's a simplicity to her melodic ideas that recalls the best aspects of nursery songs. When framed by Guthrie's gentle soundscapes, it allows "Victorialand" to evoke the sort of harmonious childhood most listeners wished for but never got.