I saw Big River at the Roundabout with the 1/2 deaf, 1/2 hearing cast. It was phenomenal!!! Let's see if I can remember exactly how they did it. Huck Finn was deaf - he signed his part. It was spoken by Mark Twain, who acted as narrator for him. As I recall, the Twain character sat DSR and spoke to the audience when he was himself, then turned US toward the Huck Finn character and spoke Huck's lines as Huck signed them. The entire production was very well done. Oh, BTW - The actor who played Twain was the original Huck Finn in the first Broadway production of Big River!