Heh. I'd heard that one even before my BiL switched his major to double-bass. (Though I think that version also made some bassists pass out, so the punchline ended "the basses are loaded with two out.") He's now thoroughly sick of it.

Though not as sick of it as his violist girlfriend is of:

You're driving down the road and see a conductor in one lane and a violist in the other. Which do you run over first?   The conductor -- business before pleasure.

---L.