There are many theories about the wide appeal and bottle-rocket rise of Beyonce Knowles, frontwoman of those new-millennial Supremes, Destiny’s Child. You have the pretty, sun-kissed face, flexible singing pipes, scantily clad girl-next-door charm and a drive that has the force (and, some allege, destructive force) of a twister.

But the real secret to the success of Beyonce, who releases her debut solo album, “Dangerously in Love,” today, is more basic. It’s all about rhythm. More than any of her twentysomething peers (Ashanti, Mya, Christina Aguilera), she understands that you can make even the most simple tune seem thrilling by toying with tempo.

When a backing track is slow and airy, Beyonce sings as if she’s playing an amphetamine-fueled game of hopscotch. When the beat speeds up, she lies back as if gently floating in a wave pool.

Such contrasts were the key to Destiny’s Child’s hits, all of which Beyonce co-wrote and produced. And they serve her well on this sparkling solo bow. Each uptempo number feels like a mini rhythm-and-blues youthquake, from the Stax-like strut of the first single, “Crazy in Love,” featuring rapper (and her current beau) Jay-Z, to the dance-hall grind of “Baby Boy” with reggae rhymer Sean Paul.

But what makes this album different from a Destiny’s Child’s set is the tone and the lyrics. On her own, Beyonce seems less interested in all-purpose anthems (“Independent Women, Pt. 1,” “Bills, Bills, Bills”) than in personal reflection.

This is especially true on the ballads, where she also showcases untapped elements of her voice. She makes like a female Ron Isley on “Speechless,” which is about the rush of sexual satisfaction. And she comes off less like a spunky teenager than a young woman with some lessons under her belt on “Me, Myself, and I.” The tune also contains one of the album’s best lines: “Love is so blind, / It feels right when it’s wrong.”

Overall, the record serves as an ideal pop/R&B model for transition and growth. Making the move from group leader to solo star can be perilous. (For every Justin Timberlake, there’s a Nick Carter.) But Beyonce said it before and it remains true: She’s a survivor.

Grade: A-