This guide is a simplified overview of all the changes in Java Edition 1.1, which assumes at least some familiarity with the Adventure Update (Java Edition 1.0.0).
The "Blocks", "Chirp", "Far", "Mall", "Mellohi", "Stal", "Strad", and "Ward" music discs are now legitimately obtainable. The "11" music disc remains unobtainable.