From the outside, Belmont native Alex Dow admits a hardcore punk show looks violent. But the community within the heart-hammering chords is one where he says anyone can feel at home. “It’s the purest form of music in the sense that, while there’s a stage and an audience, and it looks violent and crazy…It’s coming from a place of ‘everyone is equal,’” Dow said. Dow is the guitarist of Fiddlehead, a Boston-based punk band that formed in 2013. Fiddlehead is…