I don't know how long this site has been up, but there is a track by Takeharu Ishimoto (probably, since he is the composer for the game) playing in the background. I believe it's a different arrangement of one of the tracks playing in the trailer. Although I don't really like the music myself (it sounds too midi-ish for my taste), I thought people might be interested.
I'm hoping the rest of the music, not so much in style as in synth quality, ends up sounding more like the background music on the subarashiki kono sekai site. In any case it'll be interesting to see what Ishimoto comes up with.