There's never been much doubt that Mick Jones, the guitarist and principal songwriter in Foreigner, has a way with music. Nonetheless, a song as blissfully melodic as "I Want to Know What Love Is," the first single from Foreigner's "Agent Provocateur" (Atlantic 7 81999-1), still takes the listener by surprise. It isn't simply that the song is hummable; from the anthemic "Feels Like the First Time" to the poignant "Waiting for a Girl Like You," Foreigner's hits have always been tuneful in the best pop tradition. Rather, it's the hymnlike grace with which the chorus spills forth that makes the song seem an unlikely single for the band.

Foreigner, after all, first made its reputation through a mixture of heavy rock bombast and melodramatic vocalizing that capitalized on the most commercial aspects of Led Zeppelin's early '70s sound. In fact, on "Stranger in My Own House" Jones presents a perfect simulacrum of the classic Zep sound, with Lou Gramm's hyper bluesy yelp supported by thundering, John Bonham-style drums and an almost monolithic guitar riff. As millions of rock fans can attest, this formula is hard to beat.

The best moments on "Agent Provocateur," however, have nothing to do with that Led Zeppelin strategy. Instead, they rely steadfastly on making the most of Jones' melodies. "I Want to Know What Love Is" makes an ideal model, thanks to the way Jones employs whispering synthesizers and a gospel choir to emphasize the stately cadences of the chorus, but it is far from the only example. "That Was Yesterday," for instance, combines a driving, minor-key guitar figure with Gramm's keening tenor to convey a sense of anger and regret, while "A Love in Vain" uses nastily distorted power guitar to add some steel to a song of romantic remorse. In each case, Jones essentially reinvents the Foreigner sound for each new song, removing any vestiges of formula from his approach.

Unfortunately, most of the rockers on "Agent Provocateur" aren't anything but formula. "Tooth and Nail" opens the album with a brisk bit of bluster made interesting only by Jones' carefully shifting dynamics; "She's Too Tough" closes it with more of the same, only this time it's studio effects and not shifting dynamics that leavens the musical monotony. It's almost as if Jones has begun to rock by rote, using the bristling mass of his guitar sound as a substitute for musical fury.

If so, he isn't alone. In fact, Bryan Adams, the Canadian producer-songwriter-guitarist whose latest album, "Reckless" (A&M SP 5013), has become an instant favorite among the MTV crowd, has almost made an art of hard rock form without content. His song structures are predictable, rarely venturing farther afield than a fairly standard blues-inflected vocal pasted over a power-chord guitar riff. His lyrics are invariably the stuff of cliche'.

That doesn't keep his records from being catchy, mind you; in fact, a good bit of Adams' appeal stems directly from his predictability. At their best, as with his current hit, "Run to You," his songs show how easily a knowledgeable craftsman can turn a pretty tune into a catchy record through workmanlike arranging and production.

"Run to You," though, is the exception, as most of the material here verges on de'ja vu (or, more accurately, de'ja e'coute'). "Heaven," with its plodding pace and sweetly screaming guitar, delivers its melodic message like every heavy rock love ballad since the mid-'70s. "Kids Wanna Rock," with its singsong melody and de rigueur rave-ups, is virtually indistinguishable from dozens of we-love-rock songs that have gone before it. Even Adams' voice, an engaging rasp placed somewhere between John Cougar Mellencamp and Journey's Steve Perry, has an almost generic quality.

Which perhaps explains why "Reckless" packs all the passionate punch of assembly-line product. Despite Adams' carefully polished services, there's nothing underneath his music, neither heart nor soul. Even Tina Turner, who does a cameo vocal on "It's Only Love," seems anonymous in this context, which in its perverse way is the most remarkable thing about this album.

After all, even formula can prove interesting, provided you know enough to play around with it. That's the main lesson exhibited by "Thunder Seven" (MCA-5537), the latest effort by the Canadian power-trio Triumph. Unlike Foreigner or Bryan Adams, both of whom have managed consistent pop success over the past few years, Triumph is still in the process of developing a suitably commercial sound. While that has hampered the band's ability to hit big on the charts, it has left Triumph with more maneuvering room than most of its competition, and that makes all the difference on "Thunder Seven."

To begin with, Triumph isn't above flogging the same formulas as everyone else, and "Spellbound," the first single off the album, amiably thrashes its way through every cliche' in the book. Move away from songs designed expressly for the radio, however, and things get more interesting. Take, for example, "Cool Down," which starts out as just another Led Zeppelin clone, but is enlivened midway through by a charming acoustic bottleneck solo by guitarists Rik Emmett, or "Time Canon," a flatulent progressive rock melody perked up by a capella vocal arrangements.

Granted, these are tiny pleasures, especially when enjoyed at the cost of "Follow Your Heart," a shameless imitation of Boston, or "Little Boy Blues," a hokey Emmet instrumental, but they show promise. And in a style as devoted to predictability as this, even the prospect of change constitutes major news.