Music is about style as much as anything else. From prohibition flappers and early rock ’n’ rollers to hippie seekers, gutter punks, hip-hop MCs and emo kids—the freshest musical trends are defined by radical fashion and a self-possessed flair. So, whether you’re more into bellbottoms and faux fur or leather and chains, it’s time to don your finest threads and hit the scene. Here are our picks for the hottest live concerts to see and be seen this fall season in the mountains.  The Falcon in Marlboro never fails to provide a world-class lineup, but what stands out most about…