Ah. Humour is such a very subjective thing.
I wandered into a nice knicknack shop in an art centre in the city yesterday. The shop sells some of the most interesting artsy-folksy things around, which makes it a wonderful place to lose half an hour and half your current cash in. What caught my eye was a fridge magnet that says:
"Singers do it with their mouths open."
That was pure serendipity at work, for I had a chorus rehearsal within fifteen minutes of me seeing that magnet. Of course that magnet (and the one that says "Musicians do it with the conductor") got some serious chuckles in choir rehearsal that evening.
Which reminds me of other statements of similar ilk.
Statisticians probably do it.
Astronauts need space to do it.
Logicians do it symbolically.
Engineers do it with precision.
Cosmologists do it with a bang.
I'll stop now because I don't want to overdo it.