This thread made me think of a close friend, with a collection of guitars, banjos and dobros, many of which are displayed on the walls in the room adjacent to his system (10’ wide opening, between rooms). He generally has his favorite Martin acoustic, on the couch next to his listening chair (he likes to accompany). As I; he enjoys realistic SPLs, so- I mentioned this thread to him. He’s since noticed them all singing along, especially the hollow-bodied models. Of course; that just makes sense, given how acoustic resonances work. None of this is bothering him, but- I suppose it could become one of those insidious mind-worms. If it ever does: I’ll mention a felt strip, woven between the strings (per clearthinker), which would provide much damping (if thick enough). btw: Using a capo would only raise the resonant frequency/pitch, if used in the normal manner (tightly, on a fret). Applied loosely = noise.