There’s a unique tension that exists between the Mighty Mighty Bosstones and the fans in the crowd: for the guys on stage, a good show requires precision, in dress and musical performance, even movements; a good night for the mass of people rests upon the successful implementation of the exact opposite — moshing into a hot sweaty mess, riding the crowd, letting go of inhibitions and being OK with looking like a fool. The music has to be tight; the fans cannot. By that measure, and a few more, the Bosstones appearance at the 9:30 club on Saturday was a good night.