▁large ▁central ▁kn ob ▁on ▁a ▁rot ary ▁control ▁may ▁also ▁be ▁used ▁to ▁control ▁this ▁sw arm . ▁ ▁The ▁oscill ators ▁may ▁also ▁be ▁switched ▁on ▁and ▁off ▁individually ▁by ▁a ▁row ▁of ▁switch es . ▁With ▁all ▁but ▁one ▁switched ▁off , ▁the ▁instrument ▁becomes ▁a ▁simple ▁rib bon - control led ▁mon oph onic ▁synth , ▁capable ▁of ▁the ▁usual ▁gl iss and i . ▁Using ▁combinations , ▁and ▁adjust ment ▁of ▁the ▁range ▁control , ▁allows ▁a ▁non - equ id istant ▁sw ar med ▁ch ord ▁to ▁be ▁produced . ▁The ▁oscill ators ▁may ▁also ▁be ▁pres et ▁to ▁the ▁usual ▁ch ord ▁intervals ▁of ▁major ▁third s ▁etc . ▁ ▁The ▁pitch ▁control ▁also ▁controls ▁a ▁low - pass ▁filter . ▁This ▁may ▁either ▁track ▁the ▁main ▁pitch , ▁or ▁may ▁be ▁controlled ▁by ▁the ▁second ▁rib bon . ▁With ▁the ▁saw to oth ▁wave ▁of ▁the ▁oscill ators , ▁this ▁tracking ▁filter ▁controls ▁the ▁sound ▁of ▁the ▁instrument . ▁ ▁As ▁for ▁many ▁other ▁analog ue ▁synth s , ▁there ▁is ▁also ▁an ▁A DS R ▁en velope ▁control . ▁ ▁Like ▁the ▁Per se phone , ▁the ▁tun ing ▁controls ▁for ▁the ▁rib bon ' s ▁base ▁frequency ▁and ▁overall ▁range ▁have ▁such ▁a ▁wide ▁span ▁that ▁the ▁rib bon ▁controller ▁itself ▁is ▁un label led , ▁although ▁some ▁players ▁mark ▁note ▁positions ▁on ▁the ▁rib b ons ▁for ▁a ▁piece . ▁ ▁There ▁are ▁no ▁facilities ▁for ▁M ID I . ▁However ,