When “American Idol” is finally said and done in the year 2143, history will show that Carrie Underwood was the finest vocalist the talent show produced.

She has a purity and power in her voice that none of the other contestants can match. In a world where we’ve grown grateful for singers who can stay on key, Underwood’s talent would stand out in any era.  She’s able to belt without her voice losing any of its strength or fire and on her fourth album, “Blown Away,” out May 1, her confidence as a vocalist and her ability to harness her talent shines throughout, even if the quality of the songs does not.

A bonafide superstar in the country world, Underwood is getting the creme of the crop when it comes to material. Plus she’s coming up with her own ideas: she co-wrote eight of the 14 songs on here, as well as tapping into such top-tier Nashville tunesmiths (and past Underwood contributors) Hillary Lindsey, Josh Kear, Luke Laird and Chris Tompkins, and pop meisters like OneRepublic's Ryan Tedder and Mutt Lange. The result, however, is a mixed bag with the songs running the gamut from ranking among her her best to wondering who the hell let some of them on the album.

Underwood, for as wholesome as she seems, has built a good chunk of her  career on woman-done-wrong tunes, so it’s no surprised the album opens with one. The rollicking, rocking “Good Girl” is this album’s “Cowboy Casanova” and she sings the life out of it. The bad boy gets his comeuppance a few tunes in on “Two Black Cadillacs”: a tale of cheating, intrigue, duplicity, revenge and secrets that is as old as the genre itself.

On “Blown Away,” far and away the set’s best cut, Underwood returns to her Oklahoma home looking for some payback: “There’s not enough rain in Oklahoma to wash the sins out of that house/not enough wind in Oklahoma to rip the nails out of the past...shatter every window until it’s all blown away.”  It’s a powerhouse of a song and a powerhouse of a performance that packs a ominous punch similar to Martina McBride’s “Independence Day.” The listener can almost feel the barometric pressure dropping as she--and the storm she’s bringing-- get closer to her front door.

Underwood easily straddles the line between country and pop and Mark Bright’s production frequently swings fiercely into the pop world —with its vocal echoes on Underwood’s voice and the synth keyboard lines, “Blown Away” sounds like something out of ‘80s pop — and then radically shifts the other way: On “Cupid’s Got A Shotgun,” Underwood’s sassy rave-up about love’s power to wreak havoc comes complete with a heavenly host of  fiddles, mandolins and pedal steel (and great guitar work by her buddy Brad Paisley). Luckily, her singing is strong enough to serve as the glue that holds the disparate elements together.

Also, luckily, not every trip back home is as fraught with peril as “Blown Away.” If the beginning of the album features tough Carrie,  she also shows us her tender side and that you can go back home again (without a death wish). Anyone who has moved away will instantly recognize the gravitational pull that draws you into its orbit once you cross the county line on “Thank God for Hometowns.” The nostalgia doesn’t end there. If “Blown Away” is Underwood’s “Independence Day,” “Good In Goodbye” is her equivalent of Garth Brooks’ “Unanswered Prayers,” minus the high school  football game. Neither of those songs veers into the treacly. The same can’t be said of “Forever Changed,” which marks the mileposts in one woman’s life—marriage, giving birth, getting Alzheimer’s— with none of the heartbreaking grace of, say, Kathy Mattea’s “Where’ve You Been” (one of the first country songs to deal with dementia) or Patty Loveless’s “How Can I Help You Say Goodbye,” which follows along a similar lifelong trajectory.

For all of her considerable vocal prowess, it still often feels like Underwood is singing from a slight remove. She does scorned female exceptionally well, but there’s rarely the feeling of 100% vulnerability that someone like Miranda Lambert conveys (imagine Lambert singing the title track).  Plus, there’s no cohesive theme that ties the album together. It feels like random songs grouped together by type: the ferocious tunes open the album, then come the love songs, then the looking back songs, and, of course, the girl empowerment song on “Nobody Ever Told You.” Although sweet, the tune can’t hold a candle to similarly themed songs such as Christina Aguilera’s “Beautiful” or Katy Perry’s “Firework.”

While it would seem that Underwood’s voice would allow her to sing almost anything, that is not true. If there’s a slight emotional distance on some of the songs, she is miles away from sounding like she relates to the material on “One Way Ticket,” an island-swaying, toes-in-the sand ditty that, undoubtedly, is meant to be her equivalent of Rascal Flatt’s “Summer Nights” or any number of Kenny Chesney songs. She should definitely leave the flip-flips and pop tops to Chesney. As for delivering lines like “Life is like a lollipop/lick it,” well, no one on earth could sing that one convincingly (in fact, we’re hoping we misheard the lyric).

The other misstep comes at the end: From as far back as her first single  “Jesus, Take the Wheel,” Underwood has proudly declared her faith, but she’s never done it with such a weak tune as album closer “Who Are You.”  Her voice sounds fine, but the song, penned by Mutt Lange, has about as much depth as “You Light Up My Life” and is about as cloyingly generic. It’s Christian lite. God deserves better and so does Underwood.