No one attends the symphony for a surprise ending, or to watch the string section go rogue. The enjoyment lies in the way that each instrument performs as expected, to the height of the players’ abilities, creating controlled harmonies and disciplined rhythms that pull at the heart while being pleasing to the ear. So it is with Mrs. Murray’s Menagerie, the absorbing new comedy from The Mad Ones that finds six parents, each with an instantly recognizable personality, playing off one another during a market-research session at a pace that can only be described as musical.