Hello all, I'll start off by saying that I have never used alcohol to
soften hide glue joints. I have used alcohol on all of my projects to
remove lacquer and to re-stain each of my pianos, and organs. In no
instances have I seen alcohol do any damage or loosening of the joints.
Someone mentioned an Angelus, describing the pouch motors which were
used in lieu of the standard pneumatic for the key motors. The very
first piano I restored was an Angelus, and yes it was quite a difficult
mechanism to work on. The method I used was as simple as aiming a hair
dryer at each of the square pouch assemblies. I heated them to the
point of the glue bubbling out of the joint. Then it was a simple
matter of moving the parts back and forth a little and they all came
out with no damage.
To me, even if alcohol works, it seems to be a messy proposition and
could accidentally soften other joints in areas you weren't planning
Best regards to all,