[pianotech] "cracking" the unisons

[David Nereson]

Re: Ben Gac's article in the most recent Journal:  What actually 
cracks when one "cracks the unisons"?  I know, I know -- it's an 
expression -- but what in the actual procedure gave rise to the 
use of this phrase?  I still don't see how it differs from 
tuning beatless unisons.
    --David Nereson, RPT