(click picture for a video of the harp in action)
I spent some more time today and got a 5-key version working. The input circuit is very basic, just a resistor divider with the photo cell as one side of it, but it seems to work ok. There is some sort of issue that if you spread all of your fingers out on both hands and wave them across the harp as fast as possible, it will eventually send some wrong commands and screw with the receiving midi program- im not sure what is happening there, i guess that is the next thing to figure out.
The circuit is extremely messy, time to build up a board I guess.
The program code has been updated as well if that interests you.