Tuning stability and efficiency

[William Monroe]

Rex,

Consider a note where the unison is perfect, but you find the note is just a 
flea's hair flat.  Raise the right (or left, or center for that matter) 
string just that teeny bit.  No need to mute, in fact, essential not to 
mute.  You can clearly detect the slightest pitch change as the unison 
begins to waver.  Then you can raise the other two strings to match.  Your 
unison has been shimmed.

William R. Monroe


> What does "shimming open unisons" mean?
>
> Thanks.
>
> Rex Roseman