Boy without boundaries

“I feel like a lot of everything I do has been determined by me feeling like I’m a saxophone player and not really a songwriter or a singer,’’ Birnbaum says earlier this week over pizza at a restaurant near his apartment in Brooklyn. “This is the first time I feel like I’m legitimately good enough to be this.’’

And by this, he’s referring to a quixotic mix of styles and personas. Just when you have an idea of what Boy Without God is about — it’s folk, it’s experimental jazz, it’s ’60s pop, it’s art rock — the landscape shifts to a whole new view.

“I tend to jump around,’’ says Birnbaum, who’s 25. “I was obsessed with jazz when I was younger because my brother was a jazz pianist and a bit of a prodigy. I was listening to jazz all the time and thought everything else was stupid. I refused to let people listen to rock music in the band room at high school. I would literally turn off Radiohead and put on jazz. I was such a jerk.’’

At 19, he decided he was going to be a downtown New York free-jazz musician, even befriending some of the scene’s characters who would soon become his mentors. When that dream faded, he turned his attention to Boston’s music scene. His eclectic tastes paid off, playing a variety of instruments with other musicians with Boston roots, from Eli “Paperboy’’ Reed to Drug Rug and the One AM Radio.

As a bandleader, Birnbaum first made his name around here in 2006, with the Abraham Lincoln Brigade, whose “noisy, free-jazz rock’’ gave him a cult following that wasn’t exactly satisfying. “It was so inscrutable that I could have just kept doing that and kept writing the same songs over again,’’ Birnbaum says.