The needle-scratch moment—a simulation of the sound of a phonograph needle being hastily taken off a vinyl record as it’s playing—has become useful (if hackneyed) cultural shorthand for an abrupt change of direction. It is a gimmick beloved of, for instance, directors of television commercials who require a quick and (to their minds at least) funny way to let the audience know it is meant to let out a stunned, collective, “What the hey?” One doesn’t often hear the sound effect in the theater, but it is played offstage near the halfway point of Our Mother’s Brief Affair (at the Samuel J. Friedman Theatre), Richard Greenberg’s memory play about an exasperating Long Island mother (a wily and roguish Lind ...