Here, from someone who played in orchestras:
The standard of "concert A" being less than 440 HZ is still up for Baroque music played on original instruments. It's because of the technical characteristics of the instruments (lutes and violins using gut strings, harpsichord using wooden picks that can be damaged if the strings are too tensioned...etc...).
During historical periods when instrumental music rose in prominence (relative to the voice), there was a continuous tendency for pitch levels to rise. This "pitch inflation" seemed largely a product of instrumentalists' competing with each other, each attempting to produce a brighter, more "brilliant", sound than that of their rivals. (In string instruments, this is not all acoustic illusion: when tuned up, they actually sound objectively brighter because the higher string tension results in larger amplitudes for the harmonics.) MORE ABOUT IN WIKIPEDIA
The phenomenon still persist even now. I remember when I used to work in Targu-Mures State Philharmonic we got all wind and brass instruments from Yamaha (pitched at 440 HZ) and all strings players kept tunning at 442 to sound brighter... was a nightmare... they didn't want to listen us to tune normally, so we had to force instruments (pushing mouthpieces over the limit, cutting off parts of instruments, shortening the "S" of bassoons... damaging good new instruments) just because of stubbornness of wooden heads.
Vienna Symphony also tune at 442 HZ.
