Having read a few comments on the use of adhesive tape for attaching
pneumatics I restrained myself from answering.  At first I thought
that it was a joke, but then it seems that he was serious.  All I can
say is that I'm glad that he didn't come near my instruments.  It may
work, but I have seen the effects of time on different types of tape;
none of them are pretty and I would not want to deal with that on a
rebuild.  I have little respect for this idea.

Gorilla glue is a different story.  If anyone needs to repair a break
in two pieces of wood that is not air-tight, and the joint never needs
to come apart again, it is the strongest glue that I've seen.  I can
recommend it for repairing broken casework.

Just two things, as Eric said: it's extremely messy and does not come
off and make sure that it's hidden -- it is not easy to stain over.
It also expands out of the joint that you're gluing, so make sure that
(a) you clean up as you are letting it set and (b) it's not sitting
on your wife's hardwood floor or carpet.

I don't know about its flexibility for the soundboard; it may not be
ideal there, though.

Eli Shahar
Ramat Gan, Israel