The real reason things change has to do with humidity. I hate playing out doors when it gets damp or cool. , Everything changes including drums, when everything rapidly warms up outdoors you may find the finish on your guitar start to krinkle and fracture. Temperature changes mess things up fast, and strings expand/ contract accordingly. The Yamaha and other oiled finish guitars can take the beating that painted guitars can not. If you take a cold guitar inside and do not give it time to temperate stabilize you may actually hear it pop as it expands in a warm room. I have a Guitar that I purpose built because of all that , Its honduras Mahogany and Peruvian body along with a Maple set neck that does not go crazy on you in temperate changes. Bolt on necks pull hard and eventually will loosen off. Some of the newer guitar finishes expand or contract on even keel, (same rates) I have heard many people blame strings because they loose their integrity outdoors. Its mostly the woods that shift. And if you were to look at what moisture content transfers during temperate changes , it should convince you whats going on. I dare say that when a cold guitar expands from cold to warm it may expand .015" or more. The old early 70s Rock Aluminum body guitars were horrible for that , you could not keep these tuned. Bass Whaler
