To be honest I had no idea what I was doing. I am completely illiterate about music, so I could not guess* what sounds work together. It could be nice if we had a cheat sheet for it. You could put all the MellowMashes next to the corresponding circles in how to play so we could compare the sounds. And a way to access that panel from game. Probably not a problem for most people, but for me it was too dang difficult. I would like to play a game like that with a slow learning curve. First level as small as 5 sounds or even better: one level divided into sections that you know when you solved it. With harder levels the sections get longer. I like the idea and love art, but I just could not play it.
*I mean, maybe I guessed some of them correctly, but I have no idea if that's true.