“Diva Mode BGM is now available on the official website for your listening enjoyment”:http://dragon2020.sega.jp/special_miku.html.
Vocals AND lyrics if you click on the right button. Excellent.
#1 and #2 are BGM for Murakumo HQ
#3 and #4 are dragon battle themes.
These tracks are included along with the Yuzo Koshiro originals on the preorder soundtrack.