Kyle Gann, at work on a book about Ives's awesome Concord, has been blogging vigorously about the piece. Each post is worth reading and pondering. He's strongly in favor of the 1947 edition of the score, and very strongly opposed to the idea, first propagated by Elliott Carter, that Ives added dissonances in later years in order to cement his position as an innovator. "That Carter could concoct such a charge, I’ve always thought, says infinitely more about him than it does about Ives."