Bruce Snider attended his first contra dance, at Simonton Corner in Rockport, shortly after landing in the Midcoast in 1982, but don’t let that fool you. A perennial novice, he marvels at the slick moves his three sons picked up at such tender ages. Meanwhile, he stumbles happily along just trying not to gum up the works. Playing mandolin or banjo uke with his many friends in the All-Comers Band would be a high point of Bruce’s month even without the little round of applause at the end. But that doesn’t hurt either.