In reply to:
there is a reason why things are set into certain keys: because they sound better.
I would say that it goes even deeper than just a relationship to the instrument being used. the different frequency energies based around each key center will resonate with various life experiences. if D is martial, perhaps there is some correlation between the combined energy of marching(simplistic picture, I know) and the emotions necessary for battle with the frequencies most prominently found in the key of D. likewise, those keys which seem more pastoral may relate directly to the life energies found in a meadow or field. etc., etc. this may seem like a bunch of hokey, but I would like to see some thought about it. I've read(somewhere, wish I could find the source) that whale song and many natural vibrational processes(Earth's orbit) are centered around the key of Db.
anyway, I guess I believe there are connections to be found, and patterns hidden deeply within those things that move us most.
