I was playing "Allegretto in C Major" and I was told that during the stacatto decrescendo, I was supposed to slow down the tempo slightly. I listened to the CD that came with "Classical Spirit, Book 2" and I heard a slight slow down but I'm not sure that was true with every hairpin decrescendo and I didn't see any ritardandos to mark special cases.

Moreover, I can't find any information on when a pianist might want to slow down the tempo a bit during decresendos... So I was hoping that someone here would have a tip about why and when?

thanks!

As long as it doesn't completely contradict the score (assuming we aren't purists) and you like the effect, go for it! Personally, I've never heard such a rule, but can see how it could work.

Crescendo often suggests a subtle accelerando, and diminuendo frequently implies a slight rallentando or ritardando—but these associations can't always be assumed.

I came across a reference to this recently, but can't recall where! My attempt to google a source came up with an ancient text—The Principles of Expression in Pianoforte Playing, by Adolph F. Christiani (1885) (!)—but it explains the relationship well:
But lest the reader generalize, Mr. Christiani continues:
Dolmetsch Online acknowledges a connection, too:
Steven

I looked into the book reference which you posted and appreciate your research.

Based on the piece, I'm going to go with "Rule 1":

since, based on my listening-- and because the piece has two-part binary form, that would be my guess...

if you remember something about that other book, please share... ;-)

regardless,the one you cited was quite inteteresting and helpful.

There is no such rule and in fact it's to be avoided that you automatically associate playing louder with speeding up and playing slower with getting quieter. Almost all choir and orchestra conductors will have shouted at some point 'just because it's quiet doesn't mean you have to play slowly' and the same goes for piano.

Speed up or slow down as the music demands it, not because of a rule.

JohnEB,

I agree that there's no rule, and that the association shouldn't be made automatically. But there is an association nevertheless, or those choir and orchestra conductors wouldn't need to make such an admonition.

Steven