Cook's theater chops set the stage for "Idol" success.

Cook's theater chops set the stage for "Idol" success

Sure he's got the great voice, the musical smarts and daring, the cute grin, the word-nerd appeal to fellow crossword-puzzle freaks.

But David Cook had a stealth weapon, as he rose above the pack to be a co-finalist for this year's "American Idol" crown.No, it's not that strange scarf Cook often wears trailing from his back pocket like a talisman.

His special mojo: theater training.

The 25-year-old Cook may be known as a hard rocker. But he took enough acting classes, and co-starred in enough student shows, to also qualify as a true Theater Geek.

His teachers from Blues Springs, Mo., have spilled the beans on how much the adolescent David loved to belt out those Broadway show tunes.

For evidence, get thee to YouTube, where you can watch clips of the teenage Cookie playing Riff in a high-school staging of "West Side Story" and taking pratfalls ("Make 'em laugh, make 'em laugh ... ") in a student version of "Singin' in the Rain."

Cook's drama chops gave him the chutzpah to croon that schmaltzy, soaring reverie, "The Music of the Night," from Andrew Lloyd Webber's "The Phantom of the Opera" — and emerge unscathed.

Thespian versatility also gave Cook — and, to a lesser extent, third-place contestant and college drama major Syesha Mercado — a boost in other key ways.

So listen and learn, wannabe rock gods and "Idol" hopefuls. Here are some tips Cook may have picked up from his own personal "High School Musical" saga: