We used to own one but sold it quite a while ago. The Roland A800 allowed you to program sysx and connected via standard MIDI din connections. The trick on the Axx series might be that they only allow one sysx string at a time. Many of the SD90 functions expect a button "push" and "release" as two separate sysx commands. Having said that - We never actually tried the A800 with an SD90. Also, I think one of the Novation Impulse "SLxx" models might allow sysX programming? Never owned one so your mileage may vary!