There are few places in this city where you can start singing spontaneously and not be judged. One of these places is Marie’s. It’s a small, divey piano bar in a basement in the West Village where on any given night a pianist will be playing show tunes non-stop. Unless someone’s doing an obvious solo (a waitress, say), feel free to sing along. The regulars here have memorized a stupid number of songs, and, after watching them, you’ll want to as well.