[jseth]

Accurate harmonic analysis can be extremely useful for soloing or improvising over a certain set of changes... always guided by the melody of the piece, knowing "what's happening" within a song is paramount to both single note playing and re-harmonizing sections of the song to suit your desires...

I find it useful in learning a song and remembering it easily as well - and no, I don't think to myself, "okay, now there's the III min chord"... but if it's a series of chords such as a II-min7 - V7 in a different key, then it helps me approach that section more fluently. Also quite useful in composing inventions and extensions on a theme.

There ARE lots of "exceptions" (although there are rules and reasons why), and that can be frustrating... as the man who taught me harmony and theory when he was fresh out of Berklee School of Music told me - one of his professors in an advanced functional reharmonization class said, "Remember, folks, ALL of this stuff was invented by a bunch of white intellectuals who were trying to prove "why?" the Blues works..."!!!