During gameplay, pause the game, and hold L + R + Y. A row of numbers will appear representing the current song and song part. These are the meaning of the numbers:
There are 7 NiGHTS backgrounds for your PC on the disc. Just put the disc in your computer and look on the CD in the folder named "Extras" to collect your backgrounds. (There are also some on Christmas NiGHTS, and the sampler disc does not have this feature)