The first is entitled "Anniversary Music" and details updating the original game's score with a full orchestra. You can check it our here or below.
The second is entitled "Anniversary Terminals" and goes into detail on creating the Terminals for the game and a bit about 343 Guilty Spark himself. You can check this one out here or below.
And just like the updated graphics, you'll be able to listen to the original or updated score, but the option to change this will be located in the game's Options menu.