Entering Cary’s Koka Booth Amphitheatre, you pass through a wooded trail that seems pure Tolkien. But a stone arch abruptly lets out into a clearing, where you’re met by a bronze bust of former mayor Koka “The Visionary” Booth. His countenance suggests a preordained political career. An intricately cantilevered canopy above a pine deck reserved for VIPs echoes the form of the hooded stage across the broad greensward. An artificial lakecomplete with idling ducks and swanscompletes the postcard-perfect scene.

In just 90 minutes, the North Carolina Symphony will inaugurate its Summerfest, an annual series of outdoor concerts in the amphitheater. Tonight, a fleet of amateur musiciansmostly students, including some who consider teenagers oldwill join the massive professional symphony for the debut. Can there be a better recipe for anxiety? Still, somehow, complete tranquility pervades the place.

An hour before showtime, the huge cases housing concert instruments finally begin appearing backstage, like giant toads. Still, only a few people mill about. One of them is Jess Levin, who’s been a violinist with the NC Symphony since 1974. His salt-and-pepper beard and crisp diction scream (politely) “concert violinist.” Levin says the symphony has only rehearsed one time with its guests.

I’m astonished. Sure, professionals like Levin are intimately familiar with the beloved pieces on tonight’s bill: Tchaikovsky’s Violin Concerto in D Major; “Hungarian March” and the Roman Carnival Overture by Berlioz; two of Brahms’ Hungarian Dances, and Dvorák’s 9th Symphony. For the amateur musicians, this must be trial by fire.

“Sudden immersion,” Levin calls it. “We toss you in the lake and you do the best you can to attune to the group, fit in rhythmically, and everything else that’s involved in ensemble playing. It’s a quick thing, without lengthy coaching sessions. For aspiring musicians, it’s an exciting and useful experience.”

It’s nearly 7 p.m. when the amateur musicians begin arriving. Some warm up. Others just cluster in peer groups long established in other local ensembles. Any air of anticipation doesn’t impress the three conspicuously grizzled stagehands: “[Working with the symphony] adds a little culture,” says one, his tone flawlessly banal, his gaze witheringly ironic. I let them get back to watching Jean-Claude Van Damme videos online.

While “Play With the Pros” is open to amateur musicians of all ages, it predominately attracts high schoolers. There are exceptions: Following the jaunty sound of a violin, I find the Pashby family warming up. Jack is 12, Shannon is 13, and cellist Bill, who’s approximately cello-sized, is 7. They’re pleased to be here, they say, their mature manner betraying home-school discipline. They aren’t nervous. Standing with the Pashbys is Joshua Henderson, 11. “When I was in first grade,” he recalls, “the teacher made us play violin for one year, and I just loved it, so for Christmas I asked for a violin.”

Henderson beams as he says this, his long hair parted down the middle and hanging across his appealingly sunny face. He senses the value of having chosen music for himself, rather than having it thrust upon him. The Pashbys, too, seem like exactly the sort of serious but humble kids who deserve an opportunity like this. Their involvement is mostly a stroke of luck, though, as the application process is more inclusive than competitive: You fill out a basic application, pay a nominal fee and hope to get chosen by a lottery. The guest players, then, possess varying skills and investment levels. Some are here for fun. Others must have scary stage-parents lurking in the wings. Most are shockingly nonchalant about what they’re about to do.

This is certainly the case with a group of six teenagers lounging on the stone steps, who collectively radiate an air of conservatory-track savvy. When I ask about their preparations, expecting to hear about grueling practice regimens, there is a ripple of bemused laughter. Audrey Baron, an 18-year-old trumpeter from Chapel Hill with a brisk, officious manner, says she just sight-read her part at the morning rehearsal, to my obvious surprise. “I had five concerts last week,” she explains tartly, eyes narrowing. I’ve stumbled into the bivouac of battle-hardened concert veterans.

Bassoonist Joe Mullen, a 17-year-old Wake Forest resident, has a more reverent and ritualistic attitude. He’s laying out beautiful handmade reeds, a warrior deciding which talisman will bring him glory in battle. Bassoonists make their own reeds in a painstaking process that yields, according to Mullen, maybe one good reed out of every 20. For this concert, he needs a reed that can play quiet or loud equally well. Since a single reed will play differently on different days, choosing one is an almost-mystical procedure. Mullen admits the difficulty of the music and says he’s been practicing a lot on his own. “I’m trying to maybe make a statement,” he says with disarming humility.

It’s well after 7 p.m. now, and on the lawn, some of the encampments around coffee tables and beneath awnings are acquiring an air of permanency. The sun sinks behind the pines. The lake turns as green as the trees. The guests soon file onstage, in black pants and white shirts, looking rather like field trippers being herded onto an activity bus. The show begins with the Tchaikovsky violin concerto, its solo going to the winner of the 2007 Youth Concerto Competition. Gentry Lasater is a sophomore at Vanderbilt, elegantly thin in a long purple dress. She executes the famously difficult solos with confidence, ending tricky runs with triumphant flourishes of her arm. If she sometimes seems to be leading the conductor, it doesn’t do much harm to Tchaikovsky’s gorgeous music.

The program’s other works were written by composers pondering countries they didn’t call homeBerlioz on Hungary and Italy; Dvorák on America. Similarly, the night’s tourists perform with a gusto that compensates for the show’s rigid pacing. The music is brash and fun. The value of the concert depends on whether you’re looking for enthusiasm or polish.

“I loved the kids up there, sawing away,” I hear one fan say, earnestly. “Yeah, sawing away. That’s definitely what they were doing on that second piece,” replies his friend.

Hopefully, the naysayer approves of the night’s final piece, the Dvorák symphony, which the professionals play by themselves. When it is over, the venue clears out fast, and I still have one burning question: Why did Assistant Conductor Joan Landry choose such devilishly difficult music? She even refers to the Tchaikovsky piece as “the Black and Blue Concerto.” Is she trying to bruise these kids?

Turns out, Landry is not actually a sadist. Lasater won the Youth Concerto Competition with the Tchaikovsky piece. Landry built the rest of the program around it. Sitting in her dressing room, she seems laid-back for a conductor. I suppose one must be to conduct amateurs who’ve rehearsed with you once through some of the most adored pieces in the classical repertoire. She’s professional but friendly, smiling and informative. It’s nice to see a symphony let its hair down like this. Otherwise, greeting the classical generation in our ringtone world might, indeed, be a recipe for anxiety.