The .mp3 files have been re-encoded as 320kbps, but the .OGG files are well below this. This warps the sound - and makes the .mp3 files much larger than they have to be. This is a very common and understandable mistake (hence the 9). A simple re-conversion of the .OGG files while specifying what kbps the .mp3 is should resolve the issue.
I'm kind of astounded that even the original music composed for Rewritten never reaches 320kbps - I suppose this was an intentional decision to ensure the music feels the same as the original game's tracks.