It was super fun to play! I found myself humming all through the game once I got into it by the first few voice segments. Though, as Brendan said in a comment below, a voice range option like being asked for the lowest and highest comfortable tone would be super nice, since my lowest comfortable tone is still somewhat high and I was caught off-guard by having to do higher notes. Also, having to breathe in and causing the way that shapes according to pitch to spike up was a problem for me, but I'm not sure if that can be easily solved >.<
Overall a super cute game, the player character is just adorable and being encuraged to play with one's voice is a fun concept i haven't really seen much of before!