There are several glues that are useful in building and repairing of musical instruments; I will attempt a short discussion of their different merits and drawbacks,
Hot Hide Glue: used almost exclusively in the industry until the early 1960’s it’s main attributes are its ability to create a very strong bond, that dose not move when exposed to heat, it also comes apart cleanly for repair work. There is a lot of mystique concerning Hide Glue; it was certainly used on the highly coveted instruments of the past. My theory is that because it creates a thin, hard bond, it dose a superior job of allowing vibrations (string energy) to flow thru the instrument with minimal obstructions therefore increasing efficiency, I use this glue for gluing plates together and attaching braces.
The drawbacks are that because the glue has to be heated, it gels quickly at room temperature so work time is reduced to a minute or less, also it dose not like any kind of contamination on the work surfaces and because it is so thin it dose a poor job of gap filling.
Aliphatic resin (carpenters glue, whit Elmer’s glue etc.) Very common glue, it’s now used widely in the industry. This glue has a good working time, allowing adjustments to be made during glue up, it has gap filling properties that can be useful for some operations. I use this for incidental parts
The drawbacks are susceptibility to movement when exposed to even moderately hot temperatures. Imagine you guitar in its black case in your car with the air temperature in the ‘80s that can easily translate into 150 degree temperature inside the instrument case, at that point aliphatic resin can become soft enough to allow parts to shift. In my job as a repairperson I’ve seen quite a few guitars that have suffered this fate.
Polyurethane glue (Gorilla Glue) is almost as strong as epoxy, glues to just about anything, dose not impart moisture to the joint that can cause some parts to warp, when using other types of glues. Doses not creep. I use it for gluing necks together.
Epoxy great for jobs where gap filling is needed, such as gluing in carbon neck reinforcements