Wandering Beyond Time -Prologue- is the name of the theme.
Here's a youtube link I found to the song:
That one is from the PS2 version, here's the one on the PSP version:
Are we going to see more anytime soon? I'm guessing you got bored with this game, huh. I'm personally waiting on the Dulkheim theme...it has 'darkness' in the title. --- Go to Gamestop, buy a Steam card, and use it to purchase Ys Origin. You won't be disappointed. For more info: http://www.worldofys.com/yso/