ALESIS HR-16 midi and/or sysex

[did concombre]

Hello to everybody. I am did and I am a new subscriber and a long time reader 
I have successfuly bended my hr16 a while ago but now I would like to add a midi controller to be able to do stuff with my feet.
I wound like to do it with an arduino (and share it here of course) but I am not really confortable with sysex messages, I cannot understand how it really works, if the hr16 could do it from midi only and how should I formulate my sysex messages in my arduino program.
As a simple start to learn things I would like to be able to change a pattern up and down, that's all.
Does anyone know and could help? I really love this machine...
thanks anyways.
did