Illuminated button array music controllers have a long history. I was fortunate to meet the late great, Salvatore Martirano
who pioneered the construction of large button array music synthesizers. I saw him set up and play his Salmar Construction at IRCAM in the 1980's.
My modest contribution to this rich space is to enhance the illuminated button arrays (in this case from Sparkfun) with pressure sensitive resistive fabric.
I use a single "Teensy" 2.0 microcontroller to do all the led driving and key multiplexing. Sparkfun uses five chips for this where I only used one and theirs unfortunately is not wired in a way that would be easy to adapt to read pressure values from the keys.
I shared this design with Keith McMillen who went on to make piezoresistive pressure sensing products such as the Soft Step and Quneo.
I shared this design with Novation during a visit to High Wycombe to encourage them to add pressure sensitivity to their button array product (LaunchPad). They later released the LaunchPad Pro which does have it although I don't know whether they use oen of the alternatives to fabric: piezoresistive ink or molded conductive elastomers.