Thank you for your compliments and feedback! I've been thinking about the best way to add audio and visual feedback.
Currently there are particles, but they are hard to see and not the best solution. The solution I am experimenting with now is manipulating the string the notes are on.
For audio feedback, I've found it difficult to come up with a way to make meaningful audio feedback that, when implemented, will work for additional songs added. I do plan to figure out a good way and add this later.