Nicely worded, sir. I'm gonna go polish my old acoustic guitars to make them sound better than they do sound...and worth more in the process too.
Damn!!! I wish I was still in possession of that old Kay guitar circa 1965.
Impressive as the Harmony rebuild is in the upper register, the original Martin sounds much better, low to high, overall. My opinion only. Watched a few vids. Thumbs up!
Here's a question for you. Do you hear that "resonance" in the audio clip, or do you only hear it when you are playing the guitar/behind the sound hole projection?
Fine. You're not keen on taking it to a luthier. I suggested it because a reputable luthier using a borascope could easily locate an inner crack lying just beneath the surface finish of the guitar. Hope you sort it all out.
I have a similar, TC Helicon Harmonizer which may or may not be the same model you have. My unit has a "thicken button" on it, which I only toyed with once or twice. The harmonizing features works quite well, but as you stated, it sounds decent on headphones, but not so great live, or recording...
1971
Tom Dowd recorded the Allman Brothers live at Fillmore East to tape.
According to Dowd, @ wikipedia
"It was a good truck, with a 16-track machine and a great, tough-as-nails staff who took care of business,"