I just bought a used copy of the first print of FF VI Piano Collections from
http://www.vgmworld.com. The Information will be the same for the reprints. Once I get it in a couple of weeks I will post the information here (if I can search through the Japanese writing, which I can only read Hiragana and a little Katakana). There are probably fields for composer (Nobuo Uematsu), arranger (who wrote the songs for piano) and performer (whoever actually played the piano for the recordings).