Johnny Mathis and Deniece Williams.

Johnny Mathis and Jane Olivor.

Johnny Mathis and Dionne Warwick.

Sometimes you get the feeling Johnny Mathis spends his spare time lurking in the studio waiting for another pop chanteuse to record with. But then you listen to Dionne Warwick's latest album, "Friends In Love," on which Mathis appears briefly, and you realize that nothing Warwick records these days happens by chance.

It's been 10 years since Warwick's mentors, songwriters Burt Bachrach and Hal David, split up, leaving the singer with an impressive track record -- literally dozens of hits -- but a rather dubious future. And dubious soon turned dismal. The mid-'70s saw Warwick's career floundering badly. "Then Came You," just about the only bright spot, was a result of the Spinners popularity more than anything else. Year after year Warwick relinquished control of her albums to a series of producers, none of whom assembled an even faintly memorable one.

But Barry Manilow (dare a reviewer admit it?) changed all that. He put Warwick back on the charts three years ago by producing an album that, in the bargain, restored a semblance of the class, control and direction of Warwick's Bachrach and David recordings. All that was missing were the songs. And they're still missing on "Friends In Love."

Which is where Johnny Mathis comes in. The Warwick-Mathis duets help conceal these shortcomings. The title track, already a sizable hit, is a romantic ballad in the grand manner, a song that handsomely embraces two of the most enduring voices in pop music. "Got You Where I Want You" is a bit more cozy and relaxed but, as you'd expect of any Warwick-Mathis collaboration, classy just the same. Beyond the duets, though, "Friends In Love" offers few rewards.

Despite a stellar cast of songwriters, including Stevie Wonder, Tom Snow and Thomas Bell, the best Warwick can come up with is Bell's "Betcha By Golly Wow," which recalls Bachrach and David's light touch. The worst, by far, is a halfhearted attempt at funk called "A Love So Right." Warwick has never really warmed up to rhythm and blues, so any attempt at funk, no matter how commercial, seems an odd, even ludicrous choice.

Still, Warwick's husky alto often transcends her material. In the middle of the most banal song, her voice can still be magical: opaque, elusive, elegant. That voice, alone, makes owning even a decidedly mediocre album like this one worth while.

As for Jane Olivor, her concert at Wolf Trap Wednesday night is likely to be a reprise of her latest album, "In Concert," recorded live last winter in Boston. If that's the case, it will probably play better at Wolf Trap than it does on record.

For one thing, Olivor's talent simply isn't well served by a live recording. In concert she can be enchanting, possessed of a voice powerful and sublime. Her immediate and lasting rapport with an audience is also a marvel to behold. But somehow none of that really translates to vinyl. She's such a stylized vocalist that on records she often comes across sounding mannered, highly theatrical -- as if everything she sings must be rendered upon bended knee. And her choice of material -- "positive pop," she calls it -- is often no more interesting that it sounds.

Like most live albums, though, this one does offer a representative sampling of work, providing at least some basis for recommendation. The tunes range from a couple of Olivor standards (including "Carousel of Love") to John Denver's "Annie's Song" (more precious than poignant) to Gordon Lightfoot's "Weeping Willows, Cattails" (appropriately pastoral) to Grace Slick's "Seasons" (arranged a la Aznavour) to Jon Anderson's lyric for "Race to the End" from "Chariots of Fire." The last is enough to make you glad that the original soundtrack version wasn't a "talkie."

THE ALBUMS

DIONNE WARWICK -- "Friends in Love" (Arista AL9585).

JANE OLIVOR -- "In Concert" (Columbia FC37938).

THE CONCERTS

WARWICK AND JERRY BUTLER -- Friday at 8 and 11:30 at Constitution Hall

OLIVOR -- at Wolf Trap, Wednesday at 8:30.