Re: pythagorean tuning?
My guess on the point at which standardization occurred would be that it was relative to a given acoustic space (likely in Vienna, or The Vatican when the Church was conquering the world and dictating rules for artists to follow or be burned alive as heretics).
Certain frequencies would resonate better than other frequencies in the chosen structures, so to ensure that all performances were tonally pleasing, there was developed a standardized tuning and pitch range for all instruments. When the capability to measure frequencies in cycles per second came along, the common measurement was the middle A on a grand piano being 440 Hz. Since the grand piano was the only instrument that could be built that could generate the widest range of audible tones, and those tones had to be equally audible at all points in the chosen venue, that became the instrument which all others referenced. This meant that wind instruments had to be redesigned to conform to that standard.
So in essence, it came down to one person's ideology, likely a Pope instead of an artist, who decided that music would have a singular reference tone.
Probably the same mental midget who declared the progression of E to Bb was "the Devil in music".
