I took the Cap'ns question to be about overall interpretation, not nuance.
A singer might well introduce subtleties into a song each time he or she sings it - in order to keep his or her interest in a song alive, if for no other reason. However, altering the interpretation of a song at each performance is a little like setting out from London to Bristol and finding yourself on the outskirts of Birmingham. U turns on the M6 are in no way indications of good driving.
Jim Carroll