Yesterday I saw a live clip of Joe Bonamassa playing "I Woke Up Dreaming". A couple of seconds into the song I told my gf that this song reminded me of "Man of Constant Sorrow" for some reason, but it was not the rhythm, not the tempo, not the chord progression (blues in the key of F), not the tuning (standard but with capo at 1st). So today listened to MoCS and realized that that song too is in the (rather unusual for guitar) key of F. I have never played either of these songs, but I've seen "O Brother..." and heard that song a couple of times, last time I heard it was some 6 months ago. I heard the Bonamassa song for the first time yesterday. I figure the key of F is the reason I heard the similarities. Things like this have been happening to me more and more lately; I'm familiar with song A and I hear song B for the first time and immediately know what key it's in because it the same key as some Sinatra song from some record I have (or whatever I can relate the new song to). I've also noticed that I can tune up to pitch without a tuner when changing strings/doing guitar setup. I knew I have good relative pitch (intervals, chords) and just like many of us, I can usually recognize common chord forms for guitar, but I have never paid much attention to pitch. Anyone else with similar experiences? Is there any good reasons to try to develop this more or would that be a waste of time?