any of the biggest stars in modern country music carry broadly-outlined personas, the kind you can usually sum up in three words or less. Toby Keith? The swaggering alpha male. Kenny Chesney? The nostalgic beach bum. Brad Paisley? The long-suffering spouse. There’s no doubt these shorthand sketches make it easier for each artist to convey the messages in their songs. Ballad or barnburner, whiskey-laced lament or pious reverie, you have a good idea in advance how Trace Adkins or Gretchen Wilson or Jamey Johnson is going to approach it.

Tim McGraw, much like his populist hero Bill Clinton, has consistently been harder to pin down. Estrogen-satisfying heartthrobbery and slick adult-contempo moves may be particular hallmarks of McGraw’s stardom, but he’s also been able to sell himself as a scuffed-up good ‘ol boy and a restless cowboy too. Truth is, there’s no easy-to-peg encapsulation of Tim McGraw, which makes his job that much more difficult and his vocal genius that much more remarkable.

Unless they’re tackling an especially outlandish role, most country singers (especially men) tend to hew closely to their carved-in-stone personalities, letting the emotional modulations that naturally take place from one song to the next provide all the depth and dimension necessary to fill out that crudely-drawn design. McGraw prefers to work the other way around, managing to fit himself into whatever person the song demands him to be. As you’d expect, it’s a damn good way to become all things to all people.

It’s also far from easy. Not for nothing is McGraw one of the few Nashville mega-stars who gets away with taking virtually no part whatsoever in the writing of his songs. His vocal stylings are just that good, a fact made once again abundantly clear with the release of Tim’s latest album, Let It Go.

Being that McGraw’s choice of absorption over projection is decidedly trickier than its inverse, this album is no less uneven than any of his other studio efforts. When he’s hitting his marks, however, McGraw can slide with effortless ease from one headspace to another. "Whiskey and You" is a drunk’s heartbroken weeper, and Tim brings to it the kind of bitter terseness you’d expect from a man who’s bottomed out. By contrast, the moodily slick "Suspicions" calls for suave detachment, and again McGraw readily complies, coming off like an image-conscious playboy concerned that his good-looking, long-legged possession might get stolen away.

Without ever having to slip into caricature or radically alter his approach, McGraw in his best songs always manages to bring out in his performance the emotions lying dormant in the words and music. The stunning duet with wife Faith Hill, "I Need You," sounds desperate because Tim makes it desperate (not so much Hill, who compensates as a solo artist by usually getting better material than her hubby). Meanwhile, the revenge fantasy "Between the River and Me" may boast a nice funky groove, but it’s only truly exhilarating and liberating because McGraw sings it that way.

As always, McGraw’s music primarily falters when the songs themselves lack sufficient emotional content for even his considerable conjuring powers to salvage. The perpetrators here are "Last Dollar (Fly Away)," "Train #10," "Comin' Home" and the title track, dead ends no matter who sings ‘em—and tracks that’ll likely keep this record from being remembered as one of Nashville’s best in 2007.

Luckily, there are still moments when songwriting prowess and vocal mastery meet halfway, first on the evocative third-shift ode "I’m Workin’," a terrific speculative document of one late-duty cop’s scattered thoughts co-written by the peerless Lori McKenna (who also penned Faith’s amazing "Stealing Kisses"). Perhaps even better is "Kristofferson," wherein Tim finds an achingly brief good-bye note from his girl and promptly sits down to fill it out in song form, just like he imagines the titular country-folk legend would do.

It’s the closest McGraw comes to hitting a false note, ‘cause everybody knows he doesn’t write the songs. But damn if he doesn’t still make the whole world sing.