I'm going to be honest. I love the colors. I don't love that the "unique" sublegends repeat across multiple keys, and some that aren't meant to be repeats look very similar to other legends. The E, F, G, tilde, I, quotation mark, and equals sign all have essentially the same sublegend. I'd rather have less keys filled with a second legend rather than six or seven repeated legends. Just an opinion. Otherwise, I love the idea, and the majority of the execution.
Don't let me stop you, it looks like it'll be a great set. Just probably not for me.