Hello Mike, what you report is quite interesting.... Titanium alloys have a specific density hovering around 4.5. Thus they might require less energy to resonate than stainless steel, which has a density between 7.5 and 8.0.... Hence, at least in theory, stronger harmonics with Titanium Mouthpieces than stainless steel.
Tentatively extending this logic to brass, which has a density between 8.3 to 8.7, standard brass mouthpieces should sound a little darker than stainless steel ones.... But I have no idea if this is true... What is your experience?
I suspect there is more to mouthpieces being energized than metal density alone... Elasticity, and perhaps rigidity, for example, might have a role, and perhaps even ductility and malleability.
It would be interested to find out if any studies have been conducted in this area, by GW or other entities.
Regards, Guido
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