I don't want to come of too clingy, but this game astounded me in so many more ways than one, I cannot go without add my words.
From a mechanic-point of view, having one main action-button for multiple actions (interact/sing) is very simple and easy to get the hang of, and I just love minimalistic approaches like these: One singular serving multiple purposes.
The songs, as well as the graphics are beautiful and the fact the game is rythm-based adds so much potential as it involves a additional sense to the gaming experience.
I feel I wish to say more, but I believe that the more one adds, the less you take from the drawing/experience. Sometimes just let art be art.
I am having a little peformance issues (low framerate), if that may be worth taking into consideration during development, but that's about it.
I am looking forward for its release and good luck on the team!