▁to ▁give ▁the ▁most ▁pleasant ▁tone . ▁However , ▁the ▁tone ▁of ▁a ▁bell ▁is ▁mostly ▁due ▁to ▁its ▁shape . ▁A ▁bell ▁is ▁regarded ▁as ▁having ▁a ▁good ▁tone ▁when ▁it ' s ▁" in ▁t une ▁with ▁itself ". ▁In ▁western ▁bell ▁found ing , ▁this ▁is ▁known ▁as ▁" harm onic ▁tun ing " ▁of ▁a ▁bell , ▁which ▁results ▁in ▁the ▁bell ' s ▁strong est ▁harm on ics ▁being ▁in ▁harm ony ▁with ▁each ▁other ▁and ▁the ▁strike ▁note . ▁This ▁produces ▁the ▁bright est ▁and ▁pur est ▁sound , ▁which ▁is ▁the ▁attract ive ▁sound ▁of ▁a ▁good ▁bell . ▁A ▁huge ▁amount ▁of ▁effort ▁has ▁been ▁exp ended ▁over ▁the ▁centuries ▁in ▁finding ▁the ▁shape ▁which ▁will ▁produce ▁the ▁harm on ically ▁tun ed ▁bell . ▁ ▁The ▁accomp any ing ▁musical ▁st aves ▁show ▁the ▁series ▁of ▁harm on ics ▁which ▁are ▁generated ▁when ▁a ▁bell ▁is ▁struck . ▁The ▁Er furt ▁bell ▁is ▁notable ▁that ▁it ▁although ▁it ▁is ▁an ▁old ▁bell , ▁it ▁is ▁harm on ically ▁tun ed , ▁but ▁was ▁not ▁typical ▁of ▁its ▁time . ▁Pi eter ▁and ▁François ▁Hem ony ▁in ▁the ▁ 1 7 th ▁century ▁reli ably ▁cast ▁many ▁b ells ▁for ▁car ill ons ▁of ▁une qu alled ▁quality ▁of ▁tun ing ▁for ▁the ▁time , ▁but ▁after ▁their ▁death ▁their ▁guard ed ▁trade ▁secre ts ▁were ▁lost , ▁and ▁not ▁until ▁the ▁ 1 9 th ▁century ▁were ▁b ells ▁of ▁compar able ▁tun ing