The 14-year-old mosh-pitters at the front of the room ricochet off one another, goofing, self-conscious, as Caspian approach the climax of their first crescendo. It’s a secret show at the all-ages Artspace up in Gloucester, unannounced because the band wanted a chance to play live with Aaron Burke-Moran, the guitarist who’s standing in for Cal Joss on Caspian’s upcoming tour. The 26-year-old Joss is getting married in June, and he opted out of the 10,000-mile-plus trip. The room is packed, thick with hormones and incense, and the band, for the first time in years, as they admit a few hours earlier, are nervous.

Caspian came together at the tail end of 2003, but unlike most bands, guitarists Joss and Phil Jamieson, bassist Chris Friedrich, and drummer Joe Vickers cloistered themselves and practiced for almost a year before taking a stage. It shows. It shows in their new Four Trees (Dopamine), the follow-up to You Are the Conductor, and it shows even more in the emotional bombast of their live shows. Caspian, who celebrate the new disc’s release this Friday at the Paradise, are the sort of band who own the music as much as the music owns them.

Over beers at the Rhumb Line in Gloucester on the afternoon of the show, I ask Jamieson, Friedrich, and Vickers to describe their music.

Vickers: “It sounds like the Atlantic Ocean.”

Jamieson: “It’s instrumental. It’s very emotional.”

Vickers again: “It sounds like a rock band with no vocals.”

Friedrich: “Wagnerian symphonies.” The others laugh. “No, no — let me explain.”

Jamieson: “That’s the cool thing about it. It can be anything to anyone. To Chris it can be symphonic. To Joe it can be a rock band. Neither of which is wrong.”

Also true: it’s music made for overstatement. The Texas instrumental group Explosions in the Sky are the band they’re most often compared with, though Caspian are a little tired of the pairing. What they do share is a penchant for delicate, lacy guitars that sparkle, then rise, widen, and expand into shuddering torrents and gaping orgasms of sound.

It “stimulates the imagination,” Jamieson says. “To see people tap into parts of themselves that they didn’t know existed, tap into their imaginations — that’s hot shit.” He emphasizes the importance of accessing those unexplored parts — within the band, and in the audience — and the importance of “making yourself available” to discovering “the parts of yourself that have been there the whole time, dwelling.”

In the biggest, loudest part of the Gloucester set, the teenagers stop being self-conscious. They slam into each other, and they’re not laughing or playing around. They feel it too, you can tell. For a few moments, it’s not about flirting or joking. They’re lost in sound. And it’s good to see, the energy untempered, and almost scary. When the song ends, a few of them embrace, a boy and a girl, two boys. The moment’s gone. The kids high-five and get nervous and bounce into the next song a little reluctant, a little disarmed or embarrassed.

A sense of connection, of communal understanding and purpose, is quickly evident, and I wonder how it feels having someone new step in. “This is the first time I’ve been nervous in . . . ,” Jamieson breaks off. “Honestly,” he goes on, “in my opinion, he saved our band.” The emotionality of the music demands a bond; they’ve known Burke-Moran for years. “It couldn’t just be a hired gun from Craigslist,” Jamieson says. (Although he’s not touring, Joss will still write and record with Caspian.)

Caspian’s recordings are more conceptual than their live shows: it’s an opportunity for the band to focus on subtleties. Although they comprise individual songs, their albums ask to be listened to as one continuous track. But “when you see us live,” Jamieson says, “it’s a rock show. It’s going to be loud and intense, and we’re going to give 100 percent the entire time.”

Indeed. Some bands excel in the studio, others on stage. Caspian fall into the latter category. Jamieson, at 6 foot 7 inches, with a scraggly toss of hair, is a commanding stage presence. He bends at the waist, guitar low, then towers up again, swinging the guitar. In the middle of the Gloucester set, he points toward the back of the room, his gaze sharp. You have to assume he’s pointing at Joss, who’s been standing in back — a hello, a you’re-with-us-too. Vickers, in a Led Zeppelin T, is less wild-eyed than Bonzo, but he rolls big thunder on the drums, head up and blinking, as if there were snow in his face. Friedrich stands back with his bass, less animated, nodding his wool-capped head. And the new guy, Burke-Moran? He looks at times as if he were about to faint, enraptured, ecstatic, mouth wide, fuck-yeah smiling, torso banging up and down. You feel it in your chest. You feel it between your legs.

It’s sexual for them, too. Vickers on playing: “It definitely makes up for not having a girlfriend.” It’s like sex: “You’re either lost in it or you’re analyzing it.”

Jamieson wishes they could play concerts “for boys and girls who are just starting to hang out . . . I’d like to see our band with a girl.”

Vickers: “I just want to see our band.”

Friedrich: “Cal gets to do it tonight.” A fast hush falls around the table.

Seeing someone play in your stead? Vickers: “It’s like seeing your girlfriend get it on with some other dude.”

But Joss watches. At the end of the show, he stands at the back of the room, against the wall, near the door. His fiancée stands next to him. He’s smiling, but in a way that looks like it hurt. The band, sweating, make their way from the stage through the crowd, toward him. It takes a while to get there. A lot of people want to say, “Great show.”

CASPIAN + ON FIRE + CONSTANTS | Paradise Rock Club, 967 Comm Ave, Boston | April 13 | 617.931.2000