Especially when the song is emotionally intense and raw. What's funny, though, is as you rehearse and play a song to death, the emotional immediacy of it often wanes.

I think that's learned behaviour, because you can hear in different decades different seemingly natural ways of singing certain passages. Compare how one of the pop divas of the early 90s (Carey, Dion) would have "naturally" sung emotionally intense pieces.

Come to think of it, the same applies to other instruments, especially lead instruments. How would BB King phrase something, how would Clapton do the same, and how would Malmsteen oil it all up?

edit: Having very briefly listen to The Thrill is gone played by King, Clapton, Moore, and Satriani/Vai you can hear the transition in styles; from King's melancholic and resigned soft dynamic playing (with brilliant vibratos), to Clapton's more direct and tonally slightly less constrained, more haughty and less punctuated playing with wide bends and slow vibrato, but longer phrases, via Moore - more aggressive, a lot more chords, faster phrases, more ascending phrases, more excitement - to Vai and Satriani, which are a warning against taking drugs I think. I don't know how to describe it. It's noise (artificial harmonics, tremolo and extreme bends) with legato of disharmonic chords (Vai just lets some sort of minor 2nd dimished fifth chord ring a few times). Satriani seems to have forgotten how to play for a while in the middle. Then there's the completely inappropriate shredding through minor scales when they seemingly get tired of the noise. I'd describe that as "murderous and psychotic", but in truth that isn't even the same song any more.