I just read a slashdot post on how the equal tempered scale has caused people with perfect pitch to be less precise on pitches near A440. According to the post, centering the scale around A440 has made our ears less discerning of pitches near that frequency of 440Hz.
Most people don't realize it, but our musical system is based on the ratios of frequencies, and the tones that those frequencies make.
If you are a math geek or a music geek, it is quite interesting. For instance an octave above is always twice the frequency. Each interval is based on a natural ratio of frequencies.
In the olden days, they used a system where the pitches were centered around a given pitch and the ratios were maintained as perfectly as possible. This makes for the best possible resonance when you are playing in that key. Based on which note you use to start out with (which key you are playing in), the frequencies of the other notes vary ever so slightly. This makes it difficult to change from one key to another, because you have to retune each time you want to play in a different key.
In recent times, they have come up with a system that is based on an equal temperment. Essentially, each note is skewed just a little bit, so that every note is just a little bit out of tune, and each key is equally in (or out of) tune.
What I found more compelling than the post itself is in the comments below the post. If you scan through the comments, you will find a thread about whether the 12 tone scale is a human invention or not.
Incoherent07 started the discussion by posting that the 12 tone system is a human invention. I would argue that the pitches in the scale (not the temperment of the pitches) are fundamental to nature just like math is a fundamental truth of nature.
The exact frequencies of those pitches are a human decision, as is the equal temperment, but the relationship of pitches is not.
http://science.slashdot.org/article.pl?sid=07/09/04/000213
