I have the Japanese MOTHER 2 album. It’s nothing like the first one.
(For the sake of distinguishing between a CD track and a game track, I’m going to refer to the latter as “cue”, as if this were a film score.)
It’s all what you hear in the game (including a few sound samples along the way). About half of the main body of tracks are suites, meaning there are more than one cue included on the track. These usually blend smoothly into one another and are edited in certain ways to give it an “album” experience. Also, you should recognize that it leaves quite a few cues out, and some that are included are trimmed down… but that’s where the PSI Mixes come in. There are three “bonus” tracks right at the end that take a good chunk of the music missing from the rest of the album and mix them together into these crazy-but-awesome hodgepodges based on a specific theme (for instance, the first mix, “Room Number”, focuses on the music you hear in different interior locations in the game, such as Apple Kid’s house, shops, residential houses, hospitals, Dr. Andonuts’s lab, etc.). Again, hopefully you’re not looking for completion here as the PSI Mixes only use certain sections of these cues, but all in all, I would certainly recommend the MOTHER 2 album from a “listening experience” point of view.