The Files:
Beat saber uses two .json files to get info about the song.
There is a info.json file. This file is used to get info about: how the song is called, what artist, how many beats per minute and the difficulty levels there are.
The second files used are the difficulty files, these have names like: Easy.json, Hard.json and Expert.json.
This file contains the info about when and where to spawn a note and when the lights and the environment needs to be changed.
How to load the files into your game:
Its actually quite easy to load a .json file into your game.
All you need to do is create a class or multiple classes that match the data in the .json file.
This can later be used to save store the loaded data.
For Example: