tone change

[Ron Nossaman]

>Yesterday I pitch raised an old upright over 100 cents.  The tone of the 
>piano went from slightly bright to very dull.  I have seen this happen 
>before on a few unisons or maybe one section but in this case the entire 
>piano is now very dull sounding.  What causes this?  The hammers are 
>grooved, does the pitch change somehow change the string plane or spacing?
>
>chris

Chris,
File a hammer or two and find out. If they brighten back up, file the rest. 
If not, that ain't it.

Ron N