Since Yume 2kki is a game developped by a team, the soundtrack were made by several people, most of them having also contributed to the dream worlds. I don't think we could list all of the compositors - unless there's a list for it somewhere - but koronba / n3 (creator of LcdDem) and oudn (creator of Yume Graffiti) are known to have added their work to the game.