If the 9-year-old in your life hasn't alerted you already, consider this your heads up: Not since Hilary Duff has Disney delivered the masses a tween sensation as hot as the double-life-leading Miss Hannah Montana. More important for speaker-blowing second- to seventh-graders and the parents forced to buy them CDs, though, no small-screen sensation transcends the tube more convincingly. Part party girl and part plain old good girl, Montana--a sweet-voiced, playful performer--never skimps on the pipes. Country fans will chalk that up to our rhyme-named heroine's lineage; 14-year-old Miley Cyrus, who plays Montana, is the daughter of Nashville star Billy Ray Cyrus (who duets on this disc's sentimental, twang-resistant last track). The rest of the world, though, is apt to find itself belting along based on Hannah's unsinkable hooks and frothy Ashlee-meets-Hilary vocals alone: theme song "Best of Both Worlds" bumps around off a Joan Jett-reminiscent springboard; "Who Said" rips a page from the emo diaries; and "Just Like You" ladles on harmonies sweet enough to attach a stick to. Additional tracks like Jesse McCartney's "She's No You" and B5's Earth Wind & Fire redo "Shining Star" are first-rate complements to the proceedings, but make no mistake: this dance-happy hybrid belongs to the reigning pop princess alone. --Tammy La Gorce