> To listen, go to bostonglobe.com/soundtrack. Their tasks may be prosaic, but their presence is anything but. I’m talking about the many public-works landmarks in our midst. Take the multicolored natural gas tank in Dorchester, in whose brush strokes some saw a silhouette of Communist leader Ho Chi Minh. Or the massive egg-shaped digesters at the Deer Island Sewage Treatment Plant. Or the pinkish-red power plant rising out of South Boston. About 18 months ago, the Massachusetts Water Resources Authority put up a fresh beacon: a massive wind turbine on the edge of Charlestown that now looms 364 feet above the industrial corridors north of downtown. The turbine, which shares land with a sewage-pumping station, generates about $400,000 a year worth of electricity. The MWRA feeds it back into the grid in exchange for a credit toward its power costs. On a windy day, the three whirling blades, each 132½ feet long, make for a hypnotic sight, their shadows dancing across the ground underneath. The sound of the blades cutting through the air suggests waves crashing on a sandy beach, but in double time. With each revolution, we take fewer of those Boston gales for granted.