This map supposedly includes all the different sounds which are included in the original version of the game (meaning, no external resource packs are required). You can play each sound by pressing a button on a command block and there are signs with information about each sound. It’s especially useful for map makers who want to add sounds to their own maps.
As soon as you’ve spawned you will find tons of command blocks. There is a button on each block which when pressed will play the sound. You can check the command required for playing the sound by pressing the command block.
Here’s a short video which briefly shows how it works in-game.