go to the composer menu, select the memory, select the variation, ok, select the part with the strings, press Part Setting, in the Balance column set a volume of -40 for example. Exit, exit, exit, select the fill number, ok, select the part with the strings, press Part Setting, in the Balance column set a volume of -15 for example. The relative volumes between these 2 parts will remain constant irrespective of the position of the Part Balance in the Mixer.