As an addition to the above, the reason why whistling in a
theatre is considered
bad luck:
Back in the days before cans sets (integrated
headphones and a
microphone to talk to other people working
backstage) were around, the people doing the
flying would
communicate with each other with whistles. This would give them their
cues to lower or raise
scenery, or do anything else with regards to
flying.
If you were walking across the
stage, and happened to be whistling, then one of the flyers might think it was someone giving them a
cue, and you may very well get something
dropped on your
head. Of course, these days, this is not an issue, but, like so many things, it has turned into a
superstition.
If you're after any other theatre tech information, then do take a look at '
Everything you ever wanted to know about theatre tech, but were afraid to ask'