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Hi Frederik, the pitch of each note (in hertz), f = sqrt(stiffness/mass). The stiffness comes mainly from the thickness of each tongue (stiffness = t^3 and is therefore more critical than the mass), so if your drum has thicker wall section the pitch will go up and you will need longer and less wide tongues, to get the same pitch. You can make it artificially less stiff by filing it down and the tongue connection point (which is where it moves, so is the most critical place to influence the stiffness). Hope this helps. N