Thank you for an explanation of a mechanism for the short term and reversible warming-up/waking-up process that I described earlier. And now that you mentioned it, in addition to a warmer tone in my guitar that had been stored for more than 30 years I also noticed a vast abundance of overtones, certainly more than in my new Orpheum. Though this may not necessarily be perceived as an advantage for all playing styles.
Yep, just like my assumption that increased decay time would be defined as a "good" thing. That touches on the difference between archback versus flatback characteristics, and the perception that a flatback would be preferred by fingerpickers for less sustain and overtones muddying up individual notes.
Another factor coming into play generically though is that top resonance is the underlying source of all sounds and anything that increases that resonance is normally seen as a "good" thing.
Tops do get dryer (resin gets dried out too) as they get older, this makes 'em more resonant and that's also true of NCL finish.
Another method brought up before is the extended (like for a couple of years at least) "brining" of woods intended to leach out the resins/oils and create a more resonant top right from the get-go. There's evidence Stradivari did this with at least some of his wood.
Also the cellulose fibers of the wood itself become mechanically worn from flexing, this probably increases the ability of the top to resonate and might explain the "tight" sounding new top vs the broken-in top with more overtones.
Torrefaction is the latest buzzword/process which theoretically does both of the things that brining and simple aging does in a shorter time, and I can see the validity of the principle there too.
So there are a lot of mechanical physics that explain how "opening up" actually occurs, but I'm still with you on whether or not it's perceptible or necessarily a "good" thing to any given player.
What I'm getting curious about now is whether a guitar like an Orpheum that does sound so good when new will evidence "opening up" to the degree of guitars built to less exacting standards.
@ZEBOMA:
Guild also did extensive development of build techniques with the DV series (V for "Vintage") which were intended to sound "vintage" right out of the box and are pretty universally loved by their owners:
From the '97 catalog:
"...the product of years of research in how to tune the bodies and tops of these dreadnoughts to sound like vintage guitars.
...back and sides that have been sanded down...neck and endblocks have been specially selected for light weight and superior strength...top is double-A graded sitka spruce."
'Hog body DV-6's got shaved braces and top of the line DV-52 got scalloped.
In fact as far as I can tell for that year, according to the catalog, the only thing D55's got that DV-52's didn't was a wide headstock, a 3-piece neck, and the upgrade inlays on the rosette and fretboard.
I think it's been mentioned before that these would be well worth checking out unless you really want that D55 "bling". (Can't recall)