Theatre folk are, for the most part, a very superstitious lot; they will happily admit it. While many of their superstitions have their origins in reality, they hold fast long after they are necessary. Such is the case with not whistling in the theatre.
This superstition likely dates back to before the 17th century when out-of-work sailors, because of their expertise with ropes and knots, were hired to manage the fly loft – the large space above the stage into which backdrops and set pieces are hoisted out of sight or from which are dropped into place on the stage. The fly loft is managed using a system of rope lines, pulleys and counterweights. A system of whistles, much like that on a sailing ship, was used to signal the sailors to raise and lower specific pieces. Reasonably, casual whistling was banned in theatres to prevent it being accidently interpreted as a fly loft command, avoiding a weighty set piece being dropped on an actor’s head.
Today, the stage manager simple whispers into her radio headset and backdrops and set pieces glide quietly down on electric winches.
And yet, to this day, it remains bad luck to whistle in a theatre!