So the thing that has been really keeping me back on working on this project is actually knowing what I really want it to be.... Do I want it to be a MIDI Keyboard? A synth? A controller for a DAW? everything and more?

This has prevented me from designing the front panel and hence wiring everything up...I've come to the conclusion that it can be all of the things I want, but I just need to add functions one piece at a time.

I've Decided to build the project up one section at a time. It is based on a 150mm*300mm*100(w*d*h) Makerbeam frame. The units will move from left to right along the frame, with additional frames being added when needed. Each 'Unit' will communicate with the Brain via a common I2C bus, except for the Power/Comms Unit.

The Synth will begin with the following 'units':
*Synth Brain Unit-Teensy 3.6 with Teensy Audio Board with 2.8" SPI( Colour LCD, D-Pad and 2 Rotary Encoders.
*Comms/Power Unit-Handles USB Comms in, Middle In, Midi Out, and Midi Thru and has RCA Audio Out and 3.5mm Audio in.
*Slider Unit-4 Linear Potentiometers connected via PCF8591. Additional Feature could be added using the DAC of the PCF8591.
*Knob Unit-4 Rotary Potentiometers connected via PCF8591. Additional Feature could be added using the DAC of the PCF8591.
*Button Board-6 Pushbuttons connected via MCP23008 GPIO Expander Modules
*Adafruit Trellis Button Pad Unit-Featuring 2 \Adafruit Trellis Button Pads.