Hmm, I'm stunned and amazed. I have always thought of rallentando as meaning "slow this bit down (gradually) and then return to the original tempo" and ritardanto as "slow the 'base tempo' down (gradually)" IOW, slow down and stay slow. Always nice to learn something new; especially when it's something you knew (incorrectly) before. *G*

I don't have the impression that there is a difference in 'how much' to slow the tempo down between the two words. And tempo is ALWAYS a matter more of interpretation than notation.

BB,
NightWing