A piano score book of FF Ｉ- Ｘ's BGM. It's very easy to play, so you may not enjoy playing. (^^;)
This book has 6 musics from FF IV:
Theme of Love / Welcome to our Town! / Rydia / Cry in Sorrow / Hey, Cid! / Mystic Mysidia

A guitar score book of FF Ｉ- Ｘ's BGM.
I'm not sure it's hard or easy, though, DOREMI MUSIC PUBLISHING says "This book has TAB score, so beginners also can play it."
You can play 5 FF IV musics:
Welcome to our Town! / Theme of Love / Cry in Sorrow / Melody of Lute / Rydia

Piano score from FF(1) - FF XI & FF X-2.
You can play 4 FF IV musics:
The Prelude / Main Theme of Final Fantasy IV / Red Wings / Theme of Love

FF III - XI music score, arranged in music box style. This book has the score of "Aerith" music box (it was a limited item.)
2 music from FF IV :
Welcome to our Town! / Theme of Love