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 has 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.
Note also that I am using a single "Teensy" 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.