Very cool central mechanic! If I had one bit of feedback (and I recognize getting into this situation at all has more to do with me playing sloppily than anything else, but just to be aware), it would be to make sure that each pair has at least one attack that does damage. I wound up in a situation where all of my pairs were dead except for one, where all I could do was Lullaby and Cleanse, so there was no way to try to finish the fight without dying (and, funnily, both of those skills prolong the length of the fight, since one puts enemies to sleep and one heals you, making it nearly impossible to just choose to die and start over, haha).
Still, very fun, and nice music!