There are obviously highly skilled musicians who have little to no understand of music theory. Those musicians are going to play in keys that are easy for "them" to play in for the most part. Many times I have noticed old blues piano players play chords mostly in the root position. Also I have seen them play in what most of us would consider strange or difficult keys.

The last fifty years has been dominated by guitar based music. The guitar like any instrument has things that are easy to do in some keys and hard or next to impossible to do in other keys.

There are many guitar players that can sight read, but that skill is not very common.

There has been a tremendous influence from blues music across the board but in particularly in guitar music. Some of the reason for for guitar players playing in E has less to do with liking that key that copying the blues players of the past.

Having read and considered all these post, and doing some experiments, I have come to the conclusion that sharp or flat keys can not be related to "Bright" or "Melancholy"
feel in today's world of equal temperament.

One of the things that we did not address in this thread was "your" definition of "bright" and "melancholy".

To me bright means treble boost, in the 8,000 kHz - 10,000 kHz range or compression which can have the same effect in that frequency range. From an emotional prospective bright means to "me" happy, fun, content, buoyant, and several other adjectives.

Melancholy does not bring to mind a certain frequency for me. Melancholy brings to "my" mind a emotional condition of pensiveness, sadness, reflection of sadness from past events or sadness for no apparent reason.

Cheers,

Billy

“Amazing! I’ll be working with Jaco Pastorius, Charlie Parker, Art Tatum, and Buddy Rich, and you’re telling me it’s not that great of a gig?
“Well…” Saint Peter, hesitated, “God’s got this girlfriend who thinks she can sing…”