That's really rad Duane. I may take a stab at something similar in the future.
As for the echo, I'm using a Wooster Audio Space Baby. It's an echo that I absolutely love, and I started this project looking for a way to get better use of it.
I think the next step for your $5 keyboard is to get the whole thing into its own custom enclosure to make it look complete. The sounds it makes are really awesome.