Balls can be fairly explorative when out of their cage. It really depends on the individual and its mood. My adult male will roam around for a bit if I let him, but he'll eventually curl up somewhere and remain still, whether its my lap, or my bookcase (as per that photo I posted a ways back).
In comparison, corns and kings would rarely settle down....thats my opinion, anyway.
All snakes are noise-sensitive to some extent. As far as drums go, I suppose it would depend on exactly how far away they are from the snake cage. If they're like, right next to him, then I'm certain that would be pretty stressful on a regular basis. If they're on the other side of the room, the towel thing would be okay, I think.