Ah... it looks like no one else has mentioned it so...
Mitose, Katakiri, and Shimotsukin are featured in a collaboration album Voltage of Imagination Ku-Soh-Katsu-Geki. Morrigan composed Katakiri's song, as well. You can download it here: http://www.otonomai.net/forum/japanese- ... vbr-25486/
There are a whole bunch of other artists too, and the types of music are pretty much all over the place. Mitose's track is the second, and it's an awesome-sounding secret organization-like song. The album art also shows that. I have no idea what language she's singing in, but there's some English lines in it too.
Chata sings the fourth song. It's pretty nice and upbeat.
Shimotsukin sings the relaxing sixth song, which didn't impress me that much, to be honest. Even so, it's very cute and nice to listen to.
The next song is Katakiri's, and it's an eerie song with creepy instrumentals. It's actually an elegant song too, and though it has an unnerving aura, it's interesting to listen to.
Also, the album artwork is full of seifuku.