It all started with a desperate call in 2011: could he make it to Carnagie Hall on short notice and serve as the emergency replacement for Boston Symphony Orchestra conductor James Levine? Indeed, he could, and the rest is history. Now, over a year after his appointment was announced, Andris Nelsons will finally step up to the podium at Symphony Hall tomorrow night for his inaugural performance as the 15th music director in the BSO’s 133 year history. If he was nervous, he didn’t show it on Thursday morning, when the Latvian conductor invited a small group of reporters to discuss his ideas, methodology and ambitions in taking up the reigns on Huntington Ave. Here’s what you need to know:

HE’S THE PEOPLE’S MAESTRO

As the youngest BSO music director in over 100 years, Nelsons, 35, is about as far from the stuffy, snobby conductor stereotype as it gets. He’s warm and witty in conversation, and he hopes some of that youthful enthusiasm will help demystify classical music’s haughty trappings. To him, experiencing the symphony is less a highbrow luxury than a vital part of spiritual self-care, the same as nourishing the body with food or exercise. “It’s there to fulfill our souls,” he says, arguing that a night with the orchestra can provide the same thrill of a shared emotional experience (the “goosebumps,” as he says) found at a Sox or Bruins game. “This music is for everyone, for rich or poor,” says Nelsons. Describing his childhood fascination with the genre as an “infection,” he contends that his job now is to “spread the infection about how great it is to experience classical music.” In other words, don’t worry about what to wear or knowing the appropriate time to clap at the show. “Any reaction is great,” he says with a smile. “It means we have touched a person’s soul.”

HE’S IN IT TO WIN IT

Nelsons style as a conductor seems to match his personality: humble and positive, but also ambitious. In leading an elite ensemble of musicians, many of whom have more years and/or experience than their new boss, his guiding principles are respect, honesty, trust and demanding as much from himself as he does from his players. “It’s about sharing our passion for classical music at the highest level,” he says, adding that his job is “to suggest, to inspire,” rather than teach or micromanage. “It’s a mission to take care of this, it’s a privilege, and it’s not about ego.” He plans to incorporate more opera into the program (his wife Kristine Opolais is a singer and will join him to perform selections from Wagner tomorrow night) and also hopes to give works by contemporary American composers a larger platform. “It’s a combination of taking care of traditions but also looking to the future,” he says. “The music reflects how composers feel about the world. That’s important and I’m very interested in that.” And with the BSO’s robust media and tech resources marshaled around his vision, the “infection” could prove highly contagious.

HE’S GONNA BE BIG

Nelsons not only has the chops to confirm the BSO as one of the nation’s top orchesrtra, but, just as importantly, the kids are gonna love ’em. He’s personable and charming, quick to joke about his errant first pitch attempt at Fenway (Pedro Martinez told him not to throw it in the dirt, so he sent it high and wide) and rhapsodize about the “great quality of life in a very cultural city” that awaits him once he and his family get settled. There’s no hint of pandering either when he calls his new office “the best concert hall in the United States, in my opinion.” All signs point to Nelsons striking the right chord with audiences, inside and outside of Symphony Hall.