I remember Alice Gerard telling me that if it is a song, the singer chooses the key. If it is a tune, the fiddler chooses the key.

The a capella group formerly known as Soup Kitchen (and now, Bare Bones) say they do not attempt to pitch songs to the same key each time. Depending on time of day, weather, how warmed up their voices are, a song might go best in one key this morning, and another key tonight or tomorrow.

I find that is true for my voice also. It is not always a question of range. Sometimes I can be more nuanced, and seem to have more vocal flexibility in terms of tone and resonance in a lower key - sometimes in a key that is a bit higher - and that changes from day to day, from morning to evening, with how much or how long I have been singing, etc.

I ain't no real musician, but I think some keys sound "brighter" than others on instruments. I wonder if that is similar to leeneia's friend A's description of keys that 'chime' more?