[Andymcdandy]

To add to the equally tempered scale... here's a "true tempered" guitar neck.

http://www.truetemperament.com/site/index.php

Originally Posted by devellis

First, the equally tempered scale we use is a compromise that allows us to play in multiple keys with minimal tone clashing. But in any particular key, the harmonic relationship between notes isn't as sweet as it could be. So, there can be some slight dissonance relative to a just tempered scale.

Second, we all hear differently. 440 Hz doesn't sound the same to everyone. An interval that sounds perfect to one person well may not sound perfect to another. Both people may consistently choose the same interval from occasion to occasion as "perfect" yet the two people may have different perfect-sounding intervals.

A tuner measures the frequency of tones, not the subjective appraisal of those frequencies. When playing with (or perhaps even for) others, a compromise has merit. If each individual optimized tuning for his or her own subjective hearing, they may well not sound very harmonic together. So we agree on reference pitches. But if you're playing alone and you like the sound of altered pitches, or if the others you play with also like those alterations, there's no reason to adhere strictly to the reference pitches.