While not as immediately impressive as “Dust Devil,” the first track to appear from Mission of Burma’s forthcoming album, Unsound, “Second Television,” does do an exemplary job of showcasing the assembled skills of this long running, Boston post-punk band. Listen closely, and its depth is striking — Multiple, sidewinding guitar melodies, fractured bits of static, and cowbell. Yes, cowbell. Even as “Second Television” is complex in nature, these vets have enough sense not to muck things up too much. Depth is one thing and complexity for complexity’s sake is another thing. If cowbell is what’s needed for structure and to help things move along, then bring on the cowbell.