Very unique concept! I feel like it's rare for the microphone to be used as an input device in games, let alone for pitch matching, so kudos for creativity! I do feel like the singing mechanic got a bit repetitive, especially since I didn't know who I had to sing to, so I just did everybody. Maybe adding simple melodies would help give a bit of variation? Or maybe the creatures you sing to can help you spread light to others in some way? Idk just some thoughts!
The world is very pretty. The environment had a nice mystical ambiance, and all the creatures were very cute! Though the world was a bit dark for me. I get the point is that the world starts dark and lights up as you sing to creatures, though I had some trouble navigating, so maybe bump up the lighting just a bit.
Overall, great job! Love the experimental nature. It's always fun to see more unique entries.