If we’re being really band-geeky here (and I am, because I’m a classically-trained musician!) A440 is only the pitch most of us in the western world tune to. As I’ve found to my own peril (I used to play the oboe professionally), some countries in Europe don’t use A440 as the tuning standard.

In fact, some orchestras in the U.S. don’t use A440, and use A420 instead!

http://en.wikipedia.org/wiki/History_of_pitch_standards_in_Western_music#19th_and_20th_century_standards