▁playing ▁string ▁below ▁the ▁bridge ▁and ▁runs ▁up ▁to ▁the ▁p eg box ▁where ▁it ▁is ▁wrapped ▁around ▁a ▁p eg . ▁ ▁The ▁guid on ▁adjust s ▁the ▁balance ▁of ▁the ▁bridge ▁by ▁pulling ▁the ▁playing ▁string . ▁ ▁The ▁measurements ▁of ▁the ▁trom ba ▁mar ina ▁varied ▁consider ably , ▁as ▁did ▁the ▁shape ▁of ▁the ▁body ▁and ▁the ▁number ▁of ▁strings . ▁An ▁oct ave ▁string , ▁half ▁the ▁length ▁of ▁the ▁mel ody ▁string , ▁and ▁even ▁two ▁more , ▁respectively ▁the ▁tw elf th ▁and ▁the ▁double ▁oct ave , ▁not ▁rest ing ▁on ▁the ▁bridge ▁but ▁acting ▁as ▁sympath etic ▁strings , ▁were ▁sometimes ▁added ▁to ▁improve ▁the ▁tim bre ▁by ▁strength ening ▁the ▁pure ▁harm onic ▁t ones ▁without ▁increasing ▁the ▁b lare ▁due ▁to ▁the ▁action ▁of ▁the ▁bridge . ▁ ▁History ▁ ▁In ▁the ▁days ▁of ▁Michael ▁Pra et or ius ▁( 1 6 1 8 ), ▁the ▁length ▁of ▁the ▁Tr um sche it ▁was ▁ ▁and ▁the ▁three ▁sides ▁at ▁the ▁base ▁measured ▁, ▁tap ering ▁to ▁ ▁at ▁the ▁neck . ▁There ▁was ▁at ▁first ▁only ▁one ▁string , ▁generally ▁a ▁D ▁c ello ▁string . ▁The ▁heavy ▁bow , ▁similar ▁to ▁that ▁of ▁the ▁c ello , ▁is ▁used ▁between ▁the ▁highest ▁positions ▁of ▁the ▁left ▁hand ▁at ▁the ▁nod al ▁points ▁and ▁the ▁nut ▁of ▁the ▁head . ▁In ▁a ▁Tr um sche it ▁in ▁the ▁collection ▁of ▁the ▁K gl . ▁Hoch schule , ▁at ▁Charlot ten burg