Thanks for the responses!  In my own experience, which is more around furniture building, I have seen the creep described by Bill, whereby a joint _doesn't_ fail in shear because the glue had a slight amount of give.  This has tended to be either where tight vertical grain was glued to wide flat grain, like in a mass produced table top where no thought was given to wood selection or direction, or else in a large (2" +) mortice and tenon or dovetail joint where a lot cross grain is glued together from large pieces of wood.  My tail vise has about a 1/32" ridge across the dovetail joint where face piece has shrunk over the years.

Wood expansion and contraction due to moisture creates huge forces though, especially in larger pieces of wood.  Stone used to be cut by drilling rows of holes, pounding wood stakes into them and pouring water onto them.

Where things have slid on a harpsichord, any guess if it was what is usually called "white glue" which does tend to creep in normal applications (I've seen this even on 30 year old furniture bearing moderate loads), or "yellow glue", the cross linked kind (which I have not seen stress related creeping other that noted above).  It would seem that stress related creeping in an instrument with yellow glue would involve shear forces big enough to cause other problems and deformations in the instrument besides glue creep.

Thanks!

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