▁harm onic ▁content ▁of ▁a ▁musical ▁note ▁from ▁a ▁particular ▁instrument ▁or ▁the ▁harm onic ▁dist ort ion ▁of ▁an ▁ampl ifier ▁at ▁a ▁given ▁frequency . ▁ ▁Refer ring ▁again ▁to ▁Figure ▁ 2 , ▁we ▁can ▁observe ▁that ▁there ▁is ▁no ▁leak age ▁at ▁a ▁discrete ▁set ▁of ▁harm on ically - related ▁frequencies ▁sample d ▁by ▁the ▁D FT . ▁ ▁( The ▁spectral ▁null s ▁are ▁actually ▁zero - cross ings , ▁which ▁cannot ▁be ▁shown ▁on ▁a ▁log arith mic ▁scale ▁such ▁as ▁this .) ▁ ▁This ▁property ▁is ▁unique ▁to ▁the ▁rect angular ▁window , ▁and ▁it ▁must ▁be ▁appropri ately ▁configured ▁for ▁the ▁signal ▁frequency , ▁as ▁described ▁above . ▁ ▁Sym met ry ▁ ▁The ▁formulas ▁provided ▁in ▁this ▁article ▁produce ▁discrete ▁sequences , ▁as ▁if ▁a ▁continuous ▁window ▁function ▁has ▁been ▁" sample d ". ▁( see ▁an ▁example ▁at ▁Kaiser ▁window )   ▁Window ▁sequences ▁can ▁be ▁either ▁symmetric ▁or ▁ 1 - sample ▁short ▁of ▁symmetric ▁( called ▁asym metric ▁or ▁periodic ).   ▁For ▁instance , ▁a ▁symmetric ▁sequence , ▁with ▁its ▁maximum ▁at ▁a ▁single ▁center - point , ▁is ▁generated ▁by ▁the ▁M AT LAB ▁function ▁h ann ( 9 ,' sym metric '). ▁ ▁De let ing ▁the ▁last ▁sample ▁produces ▁a ▁sequence ▁identical ▁to ▁h ann ( 8 ,' period ic '). ▁ ▁An ▁even - length ▁symmetric ▁sequence ▁has ▁two ▁equal ▁center - points , ▁but ▁most ▁window ▁functions ▁used ▁in ▁practice ▁have ▁a ▁single ▁peak