I would have to formant the voices or something, since the "mudding" comes from same freq overlapping in the duets. They have never bothered me, it's part of the package in a duet that freqs might overlap here and there.
Anyway, sorry for the late reply, I've been leasing some of the instruments used here, so I would wait till I had them again. But in retro perspective, then I won't change this piece at all anyway. The loud brass also makes sure that you don't go nuts from the constant background voices. It's a camouflage.
One thing I might change tho, in retro-retro perspective, is that the voice doubling is alligned left or right, I might center that. If I can find the work file