Changes to Orchestra tuning.

Total speculation but I would expect to use a frequency that is as much in the roundhouse of as many instruments as possible.  2 hz is not a big change though I would expect if so it was determined to be a better fit.  You can look up music frequency charts online that will show you the harmonic frequency ranges of common instruments.  I have one on my wall.  It comes in very handy to help me understand what I am hearing when listening to the ol hifi better. 

I have on my wall too :).  Bought from the Vancouver Symphony, long ago  :)

Frequency ranges of individual instruments have little to do with the choosing of one tuning reference over another. As has been pointed out 2 hz is a very small change that in no way taxes the capabilities of any orchestral instrument. However, a 2 hz change can subtly alter the overall sound of an orchestra. A 2 hz downward change will cause, particularly strings, to sound slightly warmer. Conversely, a 2 hz upward change will cause the sound of an entire string section to sound slightly more brilliant since the strings have to be made tauter on the instrument. More tension on the strings will cause the instrument to sound slightly more brilliant even when playing the same pitch. Subtle, but not insignificant. Also, keep in mind that it is common, almost inevitable, that no matter what the reference tuning pitch that the oboe gives, as the orchestra plays the “communal” reference pitch will rise. As wind instruments play and warm up the pitch rises. Professional players make an effort to stay at the reference tuning pitch throughout a performance, but it is unusual for the pitch to not rise slightly.  Sometimes more than slightly.

I've never heard an Oboe give the reference. Always the 1st Violin. Am I missing something?

Yes.  

Don’t know what orchestra concerts you have attended, but the oboe always gives the tuning reference in an orchestra.  The oboe sometimes gives two tuning “A440-445”s (or whatever).  One for the winds and then one for the strings.  When it is a piano concerto the tuning reference “A” is taken from the piano on stage by the oboe and then as above.  Only when there is no oboe, in a chamber work for instance, does the first violin give it.  

@frogman Question: why the oboe in particular?

@simao , long standing tradition due to the oboe’s piercing tone which can be clearly heard and the fact that the oboe does not have an easy way to adjust its own pitch, unlike other instruments which have tuning slides or parts that can be adjusted to make longer or shorter.  So, best to tune to the instrument whose pitch will be least flexible.  

The Historically Informed movement frequently emphasizes tuning.  I wonder if the tunings they choose contribute to the occasional scratchy sounds the string players produce 

My guess is that it is specific to that hall, based on someone having ’new’ measurements made, as I say, just a guess, but I can imagine the process of getting an institution to change a fundamental, there must be a convincing argument for the change, not so convincing for the status quo

There is a chart showing the history of musical pitch here

music theory online : pitch, temperament & timbre

and there is this

history of piano tuning

Is this classical music's version of the "loudness wars?"

@bolong 

no, this is a real issue, that effects music at it (re)creation.This Loudness Wars is a mixing issue 

I was being facetious. However, increasing the string sections "brilliance" with the higher tuning might be considered an increase in "loudness."

@frogman. Very interesting re the oboe for tuning. I've often had season's subscriptions to Symphonies since the 70's.  Hundreds of concerts. Just goes to show my inattention :)  I've never paid attention until I've heard the 1st violin fire up. I'm always reading up or discussing the program. Perhaps the tones of the notes? Interesting to learn after all these years. Next visit I'll be paying attention! I hope. Thanks for your gentle information  :)   I guess the Oboe players will be working on their reeds :)  

As you know, it is standard practice for the concert master (1st violin) to enter the stage shortly before the conductor does.  He then signals to the oboe to give the “A” .  He usually remains standing while the orchestra tunes to that “A”.  Usually, the oboe then gives another A (same tuning, of course) which in theory is supposed to be just for the strings. That’s probably why you thought it was he who gave the A.  Enjoy your next concert and thanks for supporting live music!