That line between water and ice is supposed to be clear-cut — liquid above 32 degrees, solid below it. In reality, it can be a bit fuzzy. The freeze-thaw cycles throughout the winter often leave waterways, lakes, and puddles in a kind of neither-nor state. One of the best places to observe (and hear) the seam is Concord’s famed Walden Pond. I remember visiting once years ago when ice shards bobbed in the frigid water at the shore. As waves rolled toward the beach, the chunks of ice bumped together with a delicate chime-like sound I’ve never heard anywhere else. On a recent trip back, part of the pond was frozen over and part wasn’t. This time, the interplay between water and ice at the shoreline produced a quiet orchestra of cracks and crinkles — like creaky doors opening in a horror film or cellophane being peeled off pieces of hard candy. Water globules sneaked underneath sheets of ice on the pond’s surface, finding their way to the sand around the logs, twigs, and rocks frozen in place like butterflies in amber.