I found this over on TGP:
https://www.thegearpage.net/board/i...-how-can-you-tell-and-what-causes-it.1228544/
Lines up with what you are experiencing.
I think the amount of weight/mass you add to the headstock is key. The wall is a huge mass that can affect the necks vibration. A clip on tuner.... not so much.
I am not suggesting you do this, but rather thinking out loud. I suspect adding a piece of Tungsten to the headstock would probably add enough mass to have some effect (tungsten is some heavy ass material). Would probably also add enough weight to make the guitar top heavy and prone to nose dives.
Having played a guitar with titanium parts, I can tell you that Titanium nuts, saddles, and sustain blocks all have significant impact on the resonance of a guitar. They fundamentally alter the interplay between the strings and the neck/body of the guitar (They add considerable passive sustain too). The strings feel more energetic with titanium parts. Perhaps a Titanium nut or sustain block upgrade could could be your way out if this?
I realize
@Piing said that a brass sustain block did not help. I have used steel, brass, copper, tungsten, zinc alloy, and titanium sustain blocks. I have used brass, steel, stock, zinc alloy, and titanium nuts for my OFRs. Titanium is different. IME all metals beside Titanium are like a filter, they are highly biased to specific frequencies. They are eager to absorb vibrations, particularly those in specific resonance frequencies.
In my experience, Titanium is less eager to absorb sympathetic vibrations and does so with less frequency bias.
), and I think it is quite difficult to rule out effects like differences among guitars, wood, psychoacoustics, etc.
