At least I THINK they're two.

I have the complete Blue Dragon OST, but I know for sure that I lack at least two songs:

1) the instrumental version of BAD BUT BAT (the music that plays in Marumaro's village, with whistling and without vocals)
2) the english version of Watashi no Mizu to Sora (My Tears and The Sky, if I'm not mistaken)

I still haven't finished the game, so I don't know if there will be any other songs I lack.

Thanks in advance.