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Solution to this should be simple enough: if you're running your audio path in the patch example you give through a VCA in linear mode, this behavior is what you should expect. To eliminate the VCO leakage, try changing the VCA's response to exponential. You will need to adjust the envelope's "ballistics", but that should fix the VCO leak issue. If it persists after that, turn the VCA's CV level down and change the envelope so that it's outputting a hotter envelope signal into the CV input.