Sometimes, all it takes is one single to establish a pop group's stylistic identity. Certainly, that was the case with "Freak-A-Zoid," the 1983 dance hit that put Midnight Star on the pop music map because it so perfectly combined the group's technopop tendencies with its R & B roots. Coming at a time when funk and new wave were just beginning to meet on common musical ground, Midnight Star's fusion of the two couldn't have been more propitious.

No surprise, then, that there's a lot more of the same on "Planetary Invasion" (Solar 60384-1), the latest Midnight Star album. Sure, the gimmicks have changed some since last time -- instead of "Freak-A-Zoid" we get "Body Snatchers," and where the last album played off traffic cops with "No Parking (On the Dance Floor)," the new album dials up the Bell system with "Operator" -- but the basic sound is the same, from the chattering electronic pulse to Vincent Calloway's chatty vocoder. It isn't as if that's cause for complaint, either, because as the undeniably catchy "Operator" shows, Midnight Star is still capable of pulling durable dance hits from its limited bag of tricks.

What keeps the band on track through this album is its ability to keep the material fresh by reshuffling the same basic components. The intro to "Body Snatchers" announces that "Midnight Star is gonna show you 'zoids just who we are" in exactly the sort of electronic monotone that made "Freak-A-Zoid" such a sensation. But rather than replay the gambits of its predecessor, "Body Snatchers" contrasts the sonic cybernetics with rich harmony vocals and an intricate rhythm arrangement, adding a new twist to the familiar formula.

Where Midnight Star falters is in its attempts at balladry. "Let's Celebrate," for example, is a falsetto-led harmony number that somehow combines the most maudlin elements of both Earth, Wind & Fire and Kool & the Gang in a single, soppy package. Taken on its own, the song is merely unmemorable, but placed in context, it stands as an eloquent argument against messing with a successful pop music formula.

Howard Hewett knows all about formula pop; his group, Shalamar, has played music-by-numbers since its inception back in the days of disco. None of its musical identities ever quite clicked, though, until late 1982, when the group stumbled onto an inspired combination of new rock stylishness and old soul understatement. Personality conflicts caused the original lineup to crumble, however, leaving Hewett to remake Shalamar in this new image. He did an excellent job, too, as can easily be heard on the band's latest album, "Heart Break" (Solar 9 60385-1).

Initially, Shalamar was just another harmony group, but when departed member Jeffrey Daniels began moving to a harder, rock-based sound, Hewett was quick to pick up on his lead. On the new album, the central dynamic is the contrast between the rock aggression of guitarist Micki Free (Daniels' replacement) and Hewett's soulful croon. "Dancing in the Sheets," a sly song of seduction that was one of the brighter moments on the "Footloose" sound track, established the formula, as Hewett settled into a Jeffrey Osborne-style groove while Free indulged in Van Halen-ized fretboard acrobatics.

"Amnesia," however, goes the approach one better by upping the tempo and giving the whole song a strong, rock-inflected feel, and the same is true of both "Deceiver" and "Don't Get Stopped in Beverly Hills." Best of all, Shalamar isn't stuck on a single trick; "My Girl Loves Me" finds the trio settling comfortably into a chunky funk groove redolent of Rufus, while "Whenever You Need Me," a feature for the group's other new member, Delisa Davis, amply demonstrates the band's ballad ability. In all, "Heart Break" shows that Shalamar has grown from gimmickry to a genuine commitment to its music.

Then again, commitment to a new sound has risks of its own. When Skyy first busted out of Brooklyn in 1979, it boasted a fresh, guitar-based sound as well as the songwriting acumen of Brass Construction's Randy Muller. The novelty of that combination lasted only so long, though, and Skyy has had a hard time equaling the success of its 1982 hit, "Call Me."

Now that dance pop has become enamored of guitars once again, Skyy has turned up with another winner, "Dancin' to Be Dancin'," the first single from the group's new album, "Inner City" (Salsoul SA 8568). With its jangly guitar beat and semiliberated lyrics, the song catches several trends at once, making it a likable companion to both Madonna's "Like a Virgin" and Cherrelle's "I Didn't Mean to Turn You On."

"Love Is Blind" is a striking ballad featuring phrasing reminiscent of Steve Arrington, while "Slow Motion" is pleasantly lubricious, but only "Because of You" comes close to matching the appeal of "Dancin' to Be Dancin'."