Jack Johnson [ tickets ]'s Saturday (8/20) show at the Greek Theatre in Berkeley was more about setting a mood than anything else. And, at least for young college kids with Greek letters sewn across their chests, nobody sets a mood quite like Jack Johnson.

It doesn't quite add up why the 30-year-old singer-songwriter works as well as he does. He is blessed with a warming voice, knows how to pen a comforting ditty and comes across as a likeable guy. None of that, when taken individually, should be enough for him to sell out two nights at the Greek and leave fans (and scalpers) outside begging for tickets.

But Johnson is truly a case where the whole is greater than the sum of its parts.

The Hawaiian-born surfer, who directed the fine wave-riding documentary "The September Session," manages to take the mellow seaside vibe of a beach bonfire and translate it to a major amphitheater. He just strums and sings his bubbly James Taylor-meets-Dave Matthews feel-good songs like he would after a day of surfing--but instead of doing it for a group of wetsuit-wearing friends, he does it for 8,000 paying customers.

That's everybody's dream, isn't it? Take what you love to do, what you would be doing for free, and, without changing the essence, make millions of dollars off of it. In that sense, as well as in many others, Johnson has managed to plug into the Jimmy Buffett trip. Only, Jack's trip feels far more authentic than that of Mr. Parrot-head.

Opening with a gorgeous version of "Do You Remember," from this year's winning "In Between Dreams," Johnson spun mellow tales that bobbed somewhere between folk and reggae. The singer/guitarist proceeded to softly croon his way through "Posters," "Taylor," "Gone" and other selections that sounded as familiar as a friend's voice calling on the phone.

Johnson was accompanied on this night by his regular trio, drummer Adam Topol and bassist Merlo, as well as by energetic pianist Zack Gill and, in spots, by Money Mark (of Johnson's Sprout House Band project) and Dan Lebowitz (from the opener, Animal Liberation Orchestra). But, far more impressively, he was accompanied by some 8,000 back-up vocalists on nearly every verse of every song.

People sing along at other artists' shows, but it's rarely as noticeable as it is at a Johnson gig. Due to the mellow nature of his music, and a volume level that allows regular conversation during the numbers, the harmony vocals from the crowd often rise above what's being pumped from the stage. It's all part of that beachside sing-along vibe that Johnson so convincingly conjures on tracks like "Flake" and "If I Could."

Of course, Johnson has as many detractors as he has supporters. For every suburban frat boy that holds 2001's "Brushfire Fairytales" close to his heart, there's an urban hipster dressed in all black that equates Jack Johnson with Lawrence Welk. (Honestly, it's not hard to imagine Mr. Welk leading his orchestra in a bubble-rich rendition of "Bubble Toes.")

Sure, it's a bit scary to think that this singer is as close as this generation has to a true island-music hero. But that thought didn't faze this critic one bit as Johnson eased through the summery "Breakdown" and "Inaudible Memories" at the Greek. It was clear by the time he hit "Wasting Time" near the end of the show that that was exactly what this crowd hadn't been doing.