You have to edit the sound files outside of poser. Lets say you wanted characters A & B to talk back and forth in one scene. You make three sound tracks. One with only A, one with only B and one with A& B. Make mimic poses for the seperate A and B tracks. Apply pose A to A character, the pose B to b character - it doesn't matter that the first sound track will be lost, because now you add the A&B sound track that has both dialoges. To do this you need a sound editor, or most video editors can do it. I use Media Studio Pro, and Sound Forge. But there are lots of freeware sound editors that will work.