copyright 2009, The Washington Post When Carrie Underwood graduated from 'American Idol' in 2005, she wasn't greeted as a pop star so much as a supernova. Four years later, the impossibly blond 25-year-old has become a sterling glow in the Nashville starscape -- and one that isn't likely to dim with her third album, 'Play On.' It's a good-natured effort, full of bighearted ballads and cutesy revenge fantasies. But country purists will still find Underwood a tough pill to swallow: (begin ital) She was invented on television and is thereby inauthentic, (end ital) goes their grumbling, unwavering logic. Meanwhile, she continues to shine, serving hook upon genial pop hook, each adorned with the requisite honky-tonk trimmings. You can almost hear her detractors groan at 'Quitter,' a wonderfully bubbly tune imported by Swedish songsmith Max Martin. He's written ginormous hits for the likes of Britney Spears and Kelly Clarkson, and he's certainly penned the best tune here. 'Stay with me / Keeping us together,' a gleeful Underwood sings on the refrain. 'And make me feel like I never, ever want to give you up.' Ja, the lyrics are clunky, but the music feels like a Norwegian sunbeam garnished with teetering fiddles and wheezing lap steel. Similar attempts at playfulness, however, fall flat. The rock-tinged 'Cowboy Casanova' sounds like something Jon Bon Jovi has been hiding in his closet since the mid-'80s, while the opening verse of 'Undo It' reincarnates the insufferable swing of Edie Brickell's 'What I Am.' Blame current 'Idol' host (and songwriter-by-day), Kara DioGuardi for that one. She co-wrote the tune in what feels like a lame attempt to replicate another, bigger hit: Underwood's 2005 breakout single, 'Before He Cheats.' But here, Underwood doesn't sound invested in the role. So she tries again with 'Songs Like This.' After catching her man on the couch with her best friend, she forces a scowl, 'I'm surprised how easily sweet revenge rolls off my lips.' Only it doesn't. And that's the rub: The unabashed prettiness of Underwood's pipes often stifles any sense of character. Except with 'Someday When I Stop Loving You,' a smoldering ballad that opens with a haunting thought: 'One foot on the bus about half past 9 / I knew that you were leaving this time / I thought about laying down in its path / Thinking that you might get off for that.' Here, Underwood's clarion delivery feels as brutal as it is beautiful. richardsc@washpost.com 