Very nice submission! I really liked the aesthetic you achieved and the connection to the theme (no pun intended). Between the ambient music and the subtle feel of setting down those domino tiles, it was almost therapeutic. It is something I haven't done for a long time, so it was very nicely executed on that idea.
I hadn't read your webpage beforehand, so I was just starting to realize that these were different tones. I thought to myself, "Maybe I could make my own melody," and then I actually was able to, which was cool. To see that that was your intention to begin with was awesome.
If anything, I would have loved to be able to quickly choose which dominoes to use with a hotkey, just to speed up the process of making a melody—or an attempted melody, seeing as I'm not a musically inclined person.
Great idea and a nice submission.