Sand is a fluid. From wikipedia: "In physics, a fluid is a liquid, gas, or other material that continuously deforms (flows) under an applied shear stress, or e

Sand is a fluid. From wikipedia: "In physics, a fluid is a liquid, gas, or other material that continuously deforms (flows) under an applied shear stress, or external force" Sawdust may be a fluid but wood is definitely not a fluid. And in any fluid, the particles are not in any meaningful way "aligned". What you are describing with different grain sizes is similar to the behaviour of different density liquids like oil and water. They are still in no meaningful way aligned. So unless you want to claim that a guitar is a fluid, even this interpretation does not apply. What I am saying is precisely that "the fibers in the wood settle somewhat due to the vibration" is a bullshit claim spouted with utter confidence and lacking any king of evidence. I am NOT claiming that instruments do not "break in". I am asserting that this does not happen due to exposure to sound or music. I am asserting that if you do the experiment I describe, there will be no measurable difference beyond individual variation (that is why I proposed repeating the experiment on 2 * n instruments). And I assert that playing the instruments from the same experiment in a double blind listener test no one will be able to observe a difference between the 2 sets of instruments beyond just guessing. I am claiming that this whole idea is the acoustic equivalent of audiophile grade ethernet cables.