moonfesta, nostalgia, hitomi no kakera (FJY), Ashita no Keshiki, honoo no tobira (check the instrumental too) (FJY), yume no daichi, intro the world, far on the water, mo hitotsu mawashite (Pripri insert song), serenato and sandpiper
Hack SIGN is mostly Celtic goodness.
Sekai Satoyama, Sword Art Online, and Rekishi Hiwa Historia soundtracks have some Celtic and folk tracks.
Velveteen Rabbit has a couple of tracks, but I can't remember the titles. Not at home right now.
Oh vocal tracks, alright.
From hack SIGN: The world, Key of the twilight, Fake wings.
Sekai satoyama: Satoyama main theme, Earth song.
SAO: The first town, Moon and shadow.
Historia OST1: Historia opening theme, Tell me more~Opening #3, Historia closing theme.
Historia OST2: A fruitless love.
Historia OST3: Forgotten stories, A door to the past, My land.