However, there are two possible keys for every key signature. For example, the key signature of one sharp (an f#) may be that of G Major or that of e minor. {emphasis mine}
I like to think of (and subsequently hear) key centers as functions of mode. It leaves a lot more sounds available to the ear than the simple "western" major-minor perspective. Dorian, keeping with the same example, which starts on an "A" but also uses only the "f#" alteration, gives a much more uplifting, focusing... almost centering effect without need for further harmonic resolution "along the way", and it acheives this with 6 out of the same 7 tone relationships. (Not withstanding "western" intervention to alter it as per the habits of the aeolian/ionian history... in essence, robbing it of it's natural beauty or at least prostituting it to enhance thier own shortcomings)
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I say, without hesitation, that the raised sixth of the dorain scale is a *force to be reckoned with, the doorway to a different aural experience I'm reminded of as I sing it to myself...
