@Dan Maloney The chromatic button layout is intimidating at first, but after a while it makes more sense then a piano, especially for improvisation.  Its like playing up the neck on a guitar, where it really does not matter what key you are in because everything is relative.  I also think it is better because it takes up less space (4 octaves in less space then a 2 octave piano keyboard) and it has multiple ways to play the same note, which has been really fun with the single note pitch shift.  I can play unison notes and then pitch shift one and get a nice pulse.   But this one was much easier to build because of the PCB instead of doing point-to-point wiring of all of the diodes and switches.

I swear, looking at an accordion button board makes my head spin. I know there's a method to the madness, but how people figure out how to play them just baffles me. 

Do the mods you made with this version abstract away any of the (apparent) complexity?

So cool! Can't wait to hear it!

Changes from version 1:

1) I am using a printed circuit board instead of point-to-point wiring for all the switches and diodes.  So much easier!  Besides on my first prototype I have already broken a couple wires and had to fix them. Also the PCB made things much more sturdy.  I had mounting holes for the PCB that lined up with the chassis but I actually did not need any of them, having the keys pop into the chassis and be soldered into the PCB makes everything solid.  If anyone is interested I have a couple extra PCBs that I will sell at cost ($10 +shipping).

2) I upgraded from the cheap little thumb joystick to something more heavy duty and with a button and a 3rd axis.  I have not programmed anything on the 3rd axis yet but am thinking something to do with phase or amplitude manipulation with modulating frequencies

3) Instead of having a button that cycles through wave forms, I have potentiometer with 10 detents (stops). This means I can select 11 different waveforms or (once I program it) waveform combinations.  This allows me to jump to the one I want, although the analog readings from some of the positions are not always consistent.  I need to tweak the voltage readings in the case statement.  Thats what the chicken head knob is for.

4) I had the laser cutter cut out a shape of a camoose (camel moose combination).  I made a back light by enbedding a blue LED a metal shot measure that came with a bottle of tincup whisky filled up with tinfoil and 1" thick hot glue.  Before that the light from the LED was two direct, now the blue camoose glows gently in the dark.  'Blue Camoose" is a label I put on some shows I have produced or played on.

5) I added a sustain button which disables the stop note messages and changes to monophonic. This means it will pay whatever the last note pressed was until a different note is pressed or it is taken out of sustain mode.

6) This model is using the teensy audio shield instead of the DAC pin on the teensy 3.6. Sound quality is improved and I think I will be able to get past 4 note polyphony.  I am having a issues with one of the channels on the shield but it has not impacted me yet.

7) Im trying a slightly different type of keycap that I do not like as much.  Looking at other options...
 

Happy to share CAD drawings, PCB plans, or code.  I will upload a github repository once I get FM synthesis figured out.