I was watching while the tap tuning was done. After removing the hardware from the guitar, several tuning forks were tapped on the edge of a wood block to make them vibrate. Then the stem was touched to the wood top in various places around the bridge and sound holes. The tone was amplified by the guitar body. Listening carefully, the tech used a series of carving tools, inserted through the "f" holes to remove shavings of wood from the internal bracing. After a little carving, the tone was again evaluated. I could tell that the tone became louder, clearer and more pure as the work progressed. After about 3 hours there was a very obvious improvement in the instruments ability to resonate cleanly with each of the tuning forks applied in the same places. Quite a bit of wood was removed and shaken out of the body.
I was told that the more expensive instruments had this "tap tuning" done routinely and that the best guitars were deemed most benefited by the process. My guitar was noticeably different and I think, better sounding. It cost about $350. I also upgraded the pickups to the HRW model as part of the package. That was another $200 and another noticeable difference in the way it sounds. Worth it? I hope so. Jim