We're not far from the January 26, 2016 release of The Witness (PC, PS4), but going off this latest blog post from designer Jonathan Blow, there's plenty of work left to be done on the puzzling adventure. The first test readings with the actors haven't even started yet! (They begin tomorrow.)
Scanning the post, I was most interested to learn that "there is (almost) no music in the game," and there never will be. It's a stylistic choice.
According to Blow, "If we slather on a layer of music that is just arbitrarily playing, and not really coming from the world, then we're adding a layer of stuff that works against the game." So instead of focusing on that, the team "put a great deal of care into the sounds of the world around you."