Just thout I would pass along the Akai APC MIDI protocol since it seems to be so popular even though its assigned controllers cant be edited... Page 6 starts to describe the attributes of some questions raised by others...
http://6be54c364949b623a3c0-4409a68c214 ... _rev_1.pdf
MIDI output support in V7
Re: MIDI output support in V7
Needs to work with APC20 and APC40 from Roland.