Careers in the music business are generally typified by brief moments of major success preceded by "paying your dues" and succeeded by varying degrees of denouement . Friday night's double bill at Merriweather Post Pavillion provides some interesting contrasts in achieving success, and both acts are different examples of what Joni Mitchell calls "the starmaker machinery".

Kenny Loggins never seemed to pay his dues, at least publicly. His first recording attempt became a session that included former Buffalo Springfield and Poco member Jim Messina. Messina wound up "sittin' in" long enough for Loggins and Messina to become one of the most popular bands in the world.

Albums went gold and platinum faster than the band could produce them, and songs like "Your Mama Don't Dance," "Thinking of You" and "Back to Georgia" came jumping out of car radios threatening to dance across the dashboard.

Their live show was a combination of simple pop and complex instrumentations, part mugging but all musicianship. Loggins would come out first, face hidden behind a mane of hair and a full beard, but eyes alert and voice clear and evocative. He'd croon like a rock Tony Bennett sending half the audience into a swoon with compositions like "Danny's Song." Loggins was always a bit cutesy, but he never quite lapsed into a goody two-shoes and avoided parody through sheer musical talent.

Messina would then appear and soon the whole band would be stomping. Though Messina was always considered the musical heavyweight, it was Loggins who drew the visual attention. Exuberant and agile, he'd dance across the stage, happy to be there, and his mood was contagious.

Until near the end of the line.

Loggins and Messina parted as friends, but their last series of tours were wooden and bland. Occassionally a spark would fly, but the fire was out and the Loggins and Messina band called it quits before their audience quit on them.

Of course, "getting out" was a way of saying "solo" rather than "so long." People waited to hear what Messina - still considered the core of the duo's success - would do. Except Kenny Loggins stole the show.

Loggins' debut solo album was released quietly and snuck up the charts without benefit of much initial airplay. The album revealed a multi-faceted Loggins, a man capable of boogy as well ballads. His second effort, "Nightwatch," picks up where the first one left off and further enhances Loggins' solo reputation. Loggins' dues have now been publicly paid.

There's nothing particularly innovative or trend-setting about "Nightwatch." It's just a very good listen.

Producer Bob James has managed to control his penchant for smothering his artists in studio goo and let Loggins feel his own way. The result is a sharp mix of pop formulas tastefully repackaged and gift-wrapped as well-crafted presentations. Mass appeal here does not mean shlock.

The title cut and "Angelique" have the eerie undertones of more ambitious Loggins and Messina works like "pathway to Glory" and "Angry Eyes." "Somebody Knows" and "Down'n Dirty" are straight rockers with tight vocal harmonies.

There's a catch duet with Fleetwood Mac's Stevie Nicks ("Whenever I Call You Friend") that has the two sounding like the American version of Elton John and Kiki Dee. And just to show that Loggins has lost none of his zip, there's a toe-tapping cover of Joe South's "Down in the Boondocks" that is much closer to the composer's Southern/Cajun roots than Billy Joe Royal's hit version of the same tune.

Having started his solo touring as the opener for Fleetwood Mac, Loggins knows what a stage is all about from both ends of the marquee. Friday he headlines alone, but there's no reason to think his show will be anything less than his track record. After all, it seems he's always been on top.

The evening's opener, Pablo Cruise, took a much more conventional route to acceptance. They slogged around for a long time, released a critically praised but commercially disappointing first album, put out a few more records which flopped, and then - just when things were getting sticky - found the answer.

That answer, the long-waited hit single that turns unknowns into major leaguers, appeared on their last record, "A Place in the Sun." "Whatcha Gonna Do (When She Says Goodbye)" showed they could churn out a hit if necessary, but implied that the potential of their first album had been sacrified for popular success.

"Worlds Away" proves that judgment to be premature. Besides containing a followup hit ("Love Will Find a Way"), "Worlds Away" exhibits much of the improvisational prowess and textured vocal harmonies that initially caught the ear when Pablo Cruise was just a band that got some "underground FM" play. Their music is clean and tight, and they are not content to just crank out the product.

"Runnin'," "Family Man" and "You're Out to Lose" all rely on more intricate melodic patterns than your average 32-bar jukebox selection. "Don't Want to Live Without It" is a snappy piece with "single" written all over it, and there's a reasonably faithful rendition of Peter Allen's "I Go to Rio."

Live Pablo Cruise promises more than just a medley of their hits. Since they have only one and a half ("Love Will Find a Way" is still climbing), the band will have to show the audience that their new-found success is deserved. That effort should prove beneficial for everyone.